Abstract: In order to clearly indicated the resistance of tomato cultivars against Root-not nematode, artificial inoculation method of potted tomato plants was used in the greenhouse. Resistant degree against the Root-knot nematode, Meloidogyne incognita, of 17 cultivars of tomato cultivated in Jiangsu Province and surrounding districts was identified respectively. The results showed that cultivar of Tianbao 316 was high resistant, cultivars of Israel A316 and Fenguo310 were moderately resistant, cultivars of Qinying 3, Bruneau and RuixingHuamei were general resistant, cultivars of Aomiduo9, Ouyaqi and American 903 were susceptible, the rest cultivars that Suhong2003, AmericanDahong, Hezuo903, TaiwanShengnv, Duocaishuiguo, Aoli, Huangguifei and HollandZishengguo were highly susceptible. These cultivars, which contains gene Mi, show high level of resistance against root-knot nematode. All cultivars of tomato were detected for the resistance gene Mi by PCR used special primers SCAR F and SCAR R. The results indicated that 3 cultivars of the tomatoes carried homozygous Mi and the gene sequence of the Tiaobao (KF015736)、Ruixinghuamei(KF015735) and Duocaishuiguo(KF015734) had 100% homology with Heinz 1706（DQ437766）.