The activity of polygalacturonase inhibiting protein (PGIP)was assayed in four kind of cultures induced endo-polygalacturonase (endo-PG). It was discovered that endo-PG stimulated obviously the accumulation of PGIP. The PGIP contents of SuMai No. 3 and SA-Ⅱ cells,which are fungal disease-resistant,are higher than the contents of Mian Yang No. 11 and JingHua No.1. It is indicated in cell level that PGIP has relation to resistance of plant.