In order to investigate the effects of different night temperatures(16 ℃,21 ℃,26 ℃) on the rate and quality of healing in tube grafted tomato by microscopic inspection,we applied tomato (Lycopersicon esculentum Mill.) ‘Guizhen No.1’ as rootstock and ‘Zhongza No.105’ as scion.The results showed that:(1)With the increasing temperature,the layers of callus cells and diameter were increased in the graft union.More calli were observed on 5 d at 26 ℃.The diameter of grafted seedling was increased by 9.7% compared to the treatment with 16℃.(2)With the decreasing temperature,the process of vascular connection and healing was speed up.Vascular was connected on 6 d after grafting at 16 ℃ at night.The connection period was reduced by 3 d and 6 d compared to the treatments with 21 ℃ and 26 ℃,respectively.The isolation layer completely disappeared on 9 d after grafting at 16 ℃,the connection period was reduced by 3 d compared to the treatments with 21 ℃ and 26 ℃.(3)With the decreasing temperature,translocation ability of xylem and connecting force were improved.The healing quality was increased.Compared to the treatment with 21 ℃,translocation ability of xylem at 16 ℃ was induced by 12%-24%,while connecting force increased by 20%.At the same time,compared with the treatment at 26 ℃,the grafting survival rate at 16 ℃ was higher and translocation ability of xylem was induced by 19%-32%,connecting force increased by 28%,root length,volume and average diameter were increased significantly.So in the situation of 26 ℃ day temperature,16 ℃ is the best night temperature for healing of tube grafted tomato to have strong seedlings with high grafting survival rate and excellent quality.