Abstract: Abstract: China has abundant biomass resources. The total production of biomass stalks was over 0.8 billion tons in 2013 and is expected to increase in the future. It is a big challenge to utilize the abundant biomass stalks and increase their economic value. It is known that crop straw is suitable for making scrimber, which has broad market potentials. Cotton stalk is mainly composed of cellulose, hemicellulose and lignin, which is similar to wood. Due to the semi-lignified features and higher cellulose content, cotton straw is a kind of good straw biomass resource that is the alternative to wood resource. Cotton stalk scrimber has some properties which are comparable to wood-based composites, and its fabrication is a new effective way to utilize the cotton stalk resource. The processes of manufacturing crop straw scrimber included raw material preparation, extruding, drying, glue blending, lay-up, cold pressing, hot pressing and after-treatment. After being extruded, the moisture content of cotton stalk was usually over 100% (dry basis), but the appropriate moisture content was no more than 6% for the following process. So the drying process of extruded cotton stalk was very important and necessary. Compared to other drying methods, microwave drying has several advantages, such as uniform energy and high thermal conductivity to the inner of the material, energy saving, fast startup and shutdown conditions. Microwave drying also reduces the drying time. At present, microwave drying has not been applied in the drying of extruded cotton stalk because of lacking related researches, such as, mathematical modeling of the drying process, effective moisture diffusivity and drying energy. Aiming at these questions, in this study, extruded cotton stalks were dried in a domestic microwave equipment with microwave frequency of 2 450 MHz and output power of 1 kW to assess the effects of material load on drying time, drying rate, drying efficiency and specific energy consumption. Microwave drying experiments with different material loads ranging from 34 to 200 g were performed under the 1 kW microwave output power. The results showed that the drying took place mainly in the rate-falling period. A relatively long rate-falling period was observed after a short heating period and without constant rate. Among the 7 mathematical models used to fit the drying process of extruded cotton stalks, through the comparison on the R2, RMSE and sum of squares of deviations between experimental and predicted moisture ratios, it was found that the Midilli model was the best one for all the data points. The value of the drying coefficient decreased with the increase in the material load. By increasing the material load (from 34 to 200 g), the drying time increased from 10 to 20 min. To examine the effect of material load on effective moisture diffusivity, the samples in the range of 34-200 g were dried under the constant microwave output power of 1 kW. By increasing the material load of sample, the effective moisture diffusivity decreased, the average of which ranged from 1.8078×10-8-4.1997×10-8 m2/s. The activation energy was calculated using an exponential expression based on Arrhenius equation, which was 4.82 W/g. Energy consumption decreased and drying efficiency increased with the increasing of material load of extruded cotton stalks. Average specific energy consumption and drying efficiency varied in the range of 12.49-35.90 MJ/kg and 7.52%-19.78%, respectively. The results can provide the theoretic basis for the drying and industrialized production of cotton stalks.