Abstract: The study aims at improving the disease resistance of tomato varieties by inducing haumatin-like proteins gene NP24 into tomato. Through the identification of disease resistance and the activity of defensive enzyme of‘Jingle 502’,‘Naiyun 2000’and‘Bolgogragsky’, the weakest disease- resistance variety ‘Bolgogragsky’was selected to transform the NP24 gene with the Agrobacterium- mediated method. The disease index of‘Bolgogragsky’,‘Naiyun 2000’and‘Jingle 502’after 7 days of Phytophthora infestans inoculation was 81.7, 48.7 and 16.0, respectively. The activity of POD enzyme in‘Bolgogragsky’reached the peak on the first day, while that of‘Naiyun 2000’and‘Jingle 502’peaked on the 5th day, but‘Jingle 502’ had consistently higher enzyme activity than that of the other two varieties. The activity of PAL enzyme increased first and then decreased,‘Jingle 502’showed the fastest increase and the slowest decrease. ‘Bolgogragsky’showed the lowest increase and the fastest decrease. The activity of SOD enzyme in‘Jingle 502’increased on the 0-5th day and then decreased, but the activity of SOD enzyme in‘Bolgogragsky’and ‘Naiyun 2000’significantly decreased on the first day after inoculation, and displayed an increase with fluctuation on the 3rd, 5th and 7th day. The results indicated that after inoculation of Phytophthora infestans, the enzyme activities of POD and PAL in the three tomato varieties were higher than that of the control, and the enzyme activity had a negative correlation with the disease index; nevertheless, the enzyme activity of SOD in treated groups was lower than that of the control. Moreover, PCR analysis approved that NP24 gene had been transformed into the tomato genome of‘Bolgogragsky’