Abstract: In order to study the effect of the rice blast in different planting modes, through the experimental design and sampling design, the author took the pathogen of rice blast as the object of study. By catching the spore of rice blast at regular time, the author studied the relationship between the rice blast and many factors (temperature, illumination, relative humidity, different experimental interval). The experimental results showed that: the change of spore quantity of rice blast was positively correlated with temperature, illumination and relative humidity; the change of spore quantity of rice blast had a significantly positive correlation with the experimental area of same planting mode and adjoining. The study also found that the total amount of spore in diversity planting area was slightly lower than that of single planting area. It showed that the diversity planting can effectively inhibit the rice blast occurrence. At the same time, the author studied fractal dimension on the experimentation area by fractal theory. It showed that the fractal dimension was the decimal and it had some chaotic characteristics.