The effects of soil disinfectant on soil properties and soil microbial diversity and the control effect of soil disinfectant on tomato early blight were studied by using the ethanol extract of walnut peel and walnut peel residue to prepare soil disinfectant and chose dazomet as control. The results showed that the ethanol extract and walnut peel residue regulated the pH value of soil, increase the contents of hydrolyzed nitrogen, available phosphorus, available potassium and organic matter in soil, and increase the microbial diversity in soil. When using the formula（walnut peel extract∶copper sulfate∶quicklime∶rice bran∶dried chicken manure = 10∶5∶10∶10∶2） for soil disinfection,the control effect against tomato early blight was 71.9%, which was higher than dazomet. Walnut peel extract or walnut peel residue mixed with copper sulfate, quicklime, rice bran and dried chicken manure in a certain proportion could induce the increase of POD content in tomato.