Abstract: Abstract: [OBJECTIVE] The purpose of research is to induce pumpkin chromosome doubling with trifluralin.[METHOD] Method 1: the method of seed socking In the experiment germinative pumpkin seeds were socked with 0.001%,0.005% and 0.01% trifluralin solution for 4h,6h and 6h. The cell of root tip was inspected by microscope. Method 2: the method of dripping apical point With 0.001%,0.003%,0.005% and 0.01% trifluralin solution drip apical point seedling of different variety of pumpkin to induce chromosome doubling, the resut was detected with the number of chloroplast of leaf guard cells.[RESULT]The result showed that: about method 1 the best treatment for inducing tetraplont was obtained by socking seeds with 0.01% of trifluranlin solution for 6 hours, the induction frequency was 25.6%; about method 2 the result indicated that the best concentration for inducing tetraplont was the one of the 0.005% trifluralin solution, the induction frequency was 20 %.Among different variety, the induction frequency of tetraplont “Jing-hu No.1”,“Chang-qing No.1” and“2-9×1604-1”pumpkin seedling is respectively 26.7%,20% and 10%, [CONCLUSION] Trifluralin is able to induce pumpkin chromosome doubling and the sensitivity of different genotype of pumpkin to trifluralin is different.