[Objective] The study aimed to confirm the optimum grafting time of tetraploid Robinia pseudoacacia.[Method] With annual root cutting seedlings of R.pseudoacacia as rootstocks,annual tender branches grown out in early summer of tetraploid R.pseudoacacia as cions,the grafting experiment was conducted in May 10th~Aug.10th.[Result] The grafting time had obvious influence on grafting survival rate.The survival rate of grafting on Jun.20th was highest(93.6%) and that of grafting on Jul.10th was 85.2%.The graftin...