Abstract: Abstract: In order to explore the feasibility of biohythane residue application to plug production of vegetable seedlings, the effects of biohythane residue application on the physical and chemical properties of compound substrates and the growth of Brassica and Spinacia plug seedlings were investigated. Furthermore, a suitable compound substrate formula for Brassica and Spinacia seedling production were screened out. Brassica (hualv No. 4) and Spinacia (xianfeng) seedlings were grown in an experimental greenhouse located at China Agricultural University, irrigated with water once every 2 days. The biohythane residue was mixed with soil or peat, vermiculite and perlite according to different volume ratios. Twelve different substrates were tested: 100% soil (CK1), 100% biohythane residue (CK2), peat-based substrate of 50% peat, 25% vermiculite and 25% perlite (CK3), a mixture of 80% soil and 20% biohythane residue (T1), a mixture of 60% soil and 40% residue (T2), a mixture of 40% soil and 60% residue (T3), a mixture of 20% soil and 80% residue (T4), a mixture of 10% biohythane residue, 40% peat, 25% vermiculite and 25% perlite (T5), a mixture of 20% residue, 30% peat, 25% vermiculite and 25% perlite (T6), a mixture of 30% residue, 20% peat, 25% vermiculite and 25% perlite (T7), a mixture of 40% residue, 10% peat, 25% vermiculite and 25% perlite (T8), as well as a mixture of 50% residue, 25% vermiculite and 25% perlite (T9). The experiment was arranged in a randomized block design with 3 replications. The effects of biohythane residue application on seedling emergence rate, plant height, stem diameter, leaf area and seedling biomass were analysed as well as the physical and chemical properties of different substrates including bulk density, total porosity, organic matter, pH and EC values. The results indicated that the physical and chemical properties together with the growth and development of seedlings can be significantly improved by applying biohythane residue in seedling substrates. It was also suggested that compound substrates with 20% biohythane residue, 30% peat, 25% vermiculite and 25% perlite by volume (T6) were optimal to the growth and development of seedlings. Compared with CK3 (50% peat, 25% vermiculite and 25% perlite), the emergence rates of Brassica and Spinacia seedlings of T6 were significantly increased by 14.3% and 12.4%, respectively; the plant height, stem diameter and leaf area of Brassica and Spinacia seedling were all similar to or significantly higher than those of CK3; the root/shoot ratios and seedling indexes of Brassica and Spinacia seedlings between T6 and CK3 were not significantly different. With proper proportion of biohythane residue in the mixture, the root biomasses of Brassica and Spinacia seedlings were significantly increased, and the root growth could be promoted, indicating a more balanced distribution between seedling shoot and root biomasses. Consequently, with certain fertilizer efficiency, the biohythane residue can be used as one of substrate components to substitute peat partially or totally in compound substrates for leaf vegetable seedlings production. In order to increase fertilizer efficiency of the biohythane residue, aerobic composting treatment for further fermentation or combined fertilizing with nitrogen fertilizer should be considered before application.