By studying the characteristics of microbial number, nitrification and denitrification rates and respiration rate of rhizosphere soil of Brassica chinensis L. grown under the different concentration of lead (Pb) environments, the effect of lead on the ecological safety of plant rhizosphere micro-ecosystem was revealed. The results showed that the all numbers of bacteria, fungi and actinomycetes first increased and then decreased with increase of Pb concentration, and the peak value occurred in the environment with soil Pb concentration of 300mg/kg, 300mg/kg and 600mg/kg, respectively. The Pb tolerance of microbe was fungi > actinomycetes > bacteria under the Pb stress environments. The all numbers of nitrifying and denitrifying bacteria in the rhizosphere, soil nitrification and denitrification rate, and soil respiration rate also first increased and then decreased with increase of Pb concentration, and peak values of all above parameters occurred in the environment with soil Pb concentration of 300mg/kg. Nitrification rate and number of nitrifying (R2=0.6847), denitrification rate and number of denitrifying bacteria (R2=0.8511), and respiration rate and the total number of microbe (R2=06843) were all correlated significantly and positively. In conclusion, only when the soil Pb concentrations reaches or exceeds 1200mg/kg, significant microbial community structural and functional degradation of B. Chinensis rhizosphere micro ecosystem will occur.