Abstract: The effects of inorganic fertilizer on the living microbial numbers in microbial-organic-inorganic compound fertilizers were studied by indoor simulated experiment with plating count.The results showed that ammonium sulfate((NH_4)_2SO_4),ammonium dihydrogen phosphate(NH_4H_2PO_4) and potassium sulfate(K_2SO_4) were suitable inorganic fertilizers as N,P and K sources respectively for making up microbial-organic-inorganic compound fertilizer.The numbers of living microbe in microbial-organic-inorganic compound fertilizer were decreased significantly by adding(NH_4)_2SO_4,but there was less influence in the fertilizer receiving a low dose N(2%).Adding 2% to 4% P_2O_5 in form of NH_4H_2PO_4 was relatively appropriate as living microbial population in the fertilizer was larger.The addition of K_2SO_4 increased the amount of living microbes in the fertilizer,and 6% K_2O in form of K_2SO_4 was optimal.The numbers of living microbes were remarkably reduced by adding N,P,K inorganic fertilizer simultaneously,and the suitable proportion of inorganic N,P,K fertilizer was 4%N,4%P_2O_5 and 4%K_2O.