Tomato leaf mold caused by ckhdosporiwn fi~Mun Cooke often takes places dining the tomato production of protective field. Tomato wild species ware used to solve this problem in tomato breeding.This experiment was composed of four palts. Firstly, tomato leaf mold from the plastic houses oflocal area was studied by aitificia] spray inoculation, consulting N. Hubbeling physiologic race differential hosts and adopting P. Day classification system. The results indicated that there ware three races in local area, including race 123,1.3 and 3. Secondly, the seedling resistance to leaf mold of eight tomato wild species were identified by inoculating with Cladosporiwnfuh4on race 12.3 that is dominant in our region. The result showed that all these tomato wild species were resistant to race 12.3. Third1~ based on this result~ we studied dynamic changes of biochemical characters (POD, PPO. relatively conductivity rate,lignin content) in leaves of these wild species inoculated after I d,3d,5d,8d, 11 d,1 5d to find biochemical mechanism of tomato wild species resistance to Cladosporiwn fidvwn . After inoculation, generally, the peroxidase (POD) or polyphenol oxidase (PPO) activities in leaves of tested tomato wild species increased significantly in comparison with those of their control plants. Relatively conductivity rate in leaves significantly increased, especially at 1st and 3rd day after inoculation. And, lignin content in tested wild species leaves after inoculation also increased than those of the control plants. Finally, transmission and scanning electron microscope were used to study leaves of tomato wild species infected by Ckidosp~riwn fidvwn. The fiinga]gro~th on the leaves of tomato wild species was completely arrested by wild host 15 days after inoculation. Also the cell walls of leaves of tested wild species were thicker than those of susceptible variety (L402).All these made tomato wild species resisting to Cladosporiwnfidvwn.Postgraduate: Lv xiao-meiMajon Vegetable BreedingAdvisot Prof. Lijing-fu