Abstract: Using the tomato variety‘Qianxi’as experimental material,this study investigated the effects of four different photoperiods on the growth,physiological characteristics,flowering and fruiting of tomato seedlings after planting.The results showed that:（1） Compared with CK,T₃ （12 hours of WB treatment） significantly increased stem diameter,hypocotyl length,leaf length,leaf width,shoot and root dry weight,seedling index,P_n,T_r,G_s.（2） T₁,T₂ and T₃ （WB treatment at 8 h,10 h and 12h） significantly increased CAT activity compared to CK;T₂ and T₃ treatment significantly reduced the MDA content in tomato seedlings compared to CK.（3） T₁ and T₃ treatment seedlings significantly advanced the initial flowering period of the first and second spikes of tomato plants compared to CK.T₃ treatment seedling significantly increased the first and early yield of tomato plants after planting compared to CK.In summary,the 12 hours of WB treatment had promoting effects on the growth and resistance of tomato seedlings,as well as the initial flowering period and yield of tomato plants after planting.