To investigate the growth-promoting effect of interaction breeding between different crops and watermelon on watermelon seedlings,early ripening and medium-late ripening watermelon were used as materials. Four treatments were set which were interaction between watermelon and wheat,watermelon and Chinese spring onion, watermelon and garland chrysanthemum, and watermelon as the control.The growth,chlorophyll content,root activity and root absorption area of the seedlings in the period of four leaves with an apical bud were measured,and the survival time and recover period departing from the seedling bed were compared.The results showed that the interaction of the three crops and different types of watermelon seedlings could improve the root activity and chlorophyll content of seedlings.The SPAD value and root activity of the interaction treatment between medium-late ripening watermelon and garland chrysanthemum were increased by 4.94% and 68.56% respectively.The total absorption area and active absorption area of watermelon seedling roots of different interaction treatments was increased,and the survival time of the watermelon seedling was lengthened,the recovery period were shortened after bed out,and interplanting with wheat and garland chrysanthemum could prolong survival time by 1.4 to 1.9 days and shorten recover period by 0.8 to 1.2 days.Seen from the differences between crops,garland chrysanthemum had the strongest promoting effect on watermelon seedling,wheat was second and Chinese spring onion was relatively weak. Seen from the varieties of watermelon,the promoting effect of three crops on seedling showed that the medium-late ripening watermelon was better than the early ripening watermelon.