Traditional aerobic composting of cow manure is not conducive to seedling raising, and adding conditioner is an important method to improve its capability of nursery. As a byproduct of agricultural and forestry waste pyrolysis industry, wood vinegar was not been effectively used. In order to optimize the pretreatment process of cow manure aerobic compost for seedling substrate, cow dung and wheat straw were used as raw materials and wood vinegar as regulator, and adding 0, 1%, 3% and 5% of wood vinegar to the compost and putting the material into the small test reactor for fermentation. Based on the analysis of the composition of wood vinegar, its effect on the aerobic composting process was studied, and then the compost material was used for seedling test. The results showed that with the increase of the concentration, the content of water, TN, TP, K+ and organic matter degradation rate showed an upward trend, however, the pH value and EC value showed a downward trend. The relative degradation rates of cellulose and hemicellulose can be enhanced by low concentration (1%) of wood vinegar. Cucumber was selected as the test crop, and the compost material was used as substrates for germination and seedling test. The germination index of the composting extracts of all groups were more than 50%, which basically reached the nontoxic requirement of plants. The highest germination index group was 1% wood vinegar group, which was 79.17%, and in the subsequent nursery test, the seedling index (0.0449g) of the 1% wood vinegar treatment group was significantly higher than that of the other groups (P<0.05). The results of this study can provide theoretical basis and reference for optimizing the pretreatment process of cow manure aerobic composting as seedling substrate. 