Abstract: Taking tomato straw as test materials, the effects of different returning methods of tomato straw（fresh straw crushed, sun-dried and composted） on the growth of cucumber and watermelon seedlings and their allelopathy were studied in pot culture, in order to provide reference the way of fertilizer utilization of tomato straw.The results showed that within 30 days of returning tomato straw to the field, composting treatment promoted the growth of cucumber and watermelon seedlings, significantly increased the accumulation of root biomass.The fresh and dry straw returning treatments had allelopathic inhibition on the growth of cucumber and watermelon seedlings, and the fresh straw returning treatment had stronger inhibition effect, especially on the accumulation of root biomass.The inhibition effect of cucumber seedlings was stronger than that of watermelon seedlings within 30 days of returning to the field, and the inhibition effect was strengthened with the extension of returning time.The inhibition effect of watermelon seedlings was weakened after 20 days of returning.Therefore, in production, tomato straw compost should be preferentially returned to the field, and directly returned to the field（fresh sample or dry straw）.It was recommended to have a decomposition period of more than 30 days before planting melons and vegetable crops.