Abstract: The effects of spent mushroom substrates compost（A.bisporus）（SMS） and vermiculite on the growth of tomato seedlings were studied by using tomato ‘Dongnong 716’ and 50-hole seedling tray.Five culture medium were selected for this study that the physical properties meet the requirements of NY/T 2118-2012,the ratio of SMS to vermiculite were 3∶7,4∶6,5∶5,6∶4 and 7∶3 from T1 to T5,respectively; CK1（imported peat∶vermiculite=4∶6）,CK2（100% commercial substrate）,in order to provide reference for the rational utilization of SMS and solves the shortage of peat resource.The results showed that the growth of tomato seedlings were significantly affected by different culture medium, the quality of tomato seedlings in all SMS compost and vermiculite treatments was better than that of CK2.If the proportion of SMS compost was not appropriate, the growth of tomato seedlings would be inhibited.The quality of tomato seedling and substrate was the best in T3（SMS compost∶vermiculite=5∶5）,next one was T2 treatment（SMS compost∶vermiculite=4∶6）.Both the strong seedling index and the comprehensive index were the ideal parameters to measure the culture medium quality.Available nutrient, bulk density, total porosity and gas-water ratio were the important factors affecting the quality of culture medium.In a word, SMS（A.bisporus） compost is an ideal culture medium, which can replace peat for tomato seedling cultivation, and can be used for tomato breeding factory.