The effect of chlorobenzene and nitrophenol on soil biological activity was studied through analyzing soil respiration intensity, microbial numbers and soil enzyme activities. The results showed that the effect of chlorobenzene and nitrophenol on soil biological activity was complex. Chlorobenzene below 200mg/kg could stimulate soil respiration and total numbers of bacteria, actinomyces and fungi, but inhibit amoniafying bacteria, nitrifying bacteria and denitrifying bacteria. The chlorobenzene below 200mg/kg also stimulated the activities of urease and dehydrogenase but slightly inhibited the activity of sucrase. Nitrophenol below 200mg/kg inhibited the growth of almost all microbes and the activities of several enzyme.