Abstract: Abstract: Saline-alkaline stress (SAS) is one of the major abiotic stresses affecting the growth of plants. It has been a severe problem that restricts plant production and even the development of the ecological environment. The improvement of plant saline-alkaline tolerance and selection of saline-alkaline tolerance plant varieties are becoming hot spots for research. To develop and select saline-alkaline tolerance plants, an evaluation method that can accurately judge the plant saline-alkaline tolerance must be first established. In the present study, the evaluation of saline-alkaline tolerance of plants is generally based on morphological indicators and physiological and biochemical indicators. These evaluation methods require a large number of samples and long cycle, and cannot be early diagnosed. Moreover, many of the indicators must be obtained through the destructive measurement of test-tube experiments, which are not nondestructive testing. Therefore, the traditional evaluation method has many disadvantages. In order to explore the methods of early, sensitive, in situ and nondestructive testing saline-alkaline tolerance of plants, a complex solution consisting of NaCl, Na2SO4, NaHCO3 and Na2CO3 with pH value of 9.09 was used to stress 2 kinds of maize variety seedlings of Zhengdan 958 with poor saline-alkaline tolerance and Mingyu 20 with strong saline-alkaline tolerance. Time-domain waveforms of leaf electrical signals of Zhengdan 958 and Mingyu 20 seedlings during saline-alkaline stress were collected. The marginal spectra of 2 kinds of maize leaf electrical signals were obtained by Hilbert-Huang transformation (HHT). The changes of marginal spectrum entropy (MSE) of maize leaf electrical signals and the biological significance were analyzed. The results showed that the MSE of leaf electrical signals from maize variety Zhengdan 958 continued to decline in the process of saline-alkaline stress, while the MSE of leaf electrical signals from maize variety Mingyu 20 changed in volatility. It was indicated that the ion transport of leaf cells in Zhengdan 958 was inhibited under saline-alkaline stress, and there was complex metabolic regulation in leaf cells of Mingyu 20 to maintain the dynamic balance of ion transport and normal functional status of leaf cell. The study also found that the malondialdehyde (MDA) content in leaf of Zhengdan 958 was increasing in the process of saline-alkaline stress, and the MDA content in leaves of Mingyu 20 began to increase significantly after 4 days of stress. This phenomenon suggested that there was membrane lipid peroxidation in leaves of Zhengdan 958 in the early stages of saline-alkaline stress, and it was more and more serious with the process of the stress, however, there was significant membrane lipid peroxidation in leaves of Mingyu 20 after 4 days of stress. The membrane lipid peroxidation of leaf cells caused by saline-alkaline stress could be the reason to the decrease of MSE about maize leaf electrical signals. Due to that the variation of the MSE from 2 maize varieties with different saline-alkaline tolerance under saline-alkaline stress was different, the response index (RI) of electrical signal based on the MSE was defined in this paper. The results showed that the RI values of maize varieties Zhengdan 958 and Mingyu 20 were obviously different in the processes of saline-alkaline stress. The influence of saline-alkaline stress on the ion transport and cell membrane injury of maize leaf cell could be sensitive and early quantitatively diagnosed according to the size of RI, and then to achieve in situ measurement and nondestructive evaluating saline-alkaline tolerance of maize seedlings. Since the RI based on plant electrical signals has not relationship with the species, the method proposed in this paper to evaluate the saline-alkaline tolerance of maize seedlings may also have a wide range of applicability. It is expected that the evaluation method about saline-alkaline tolerance of plant proposed in this paper can be verified through a large number of experiments.