With pepper（Capsicum annuum L.）variety Longjiao 10s cultural substrate［cultural substrate formula for corn straw∶cow dung∶mushroom residue∶slag=2.5∶2.0∶2.0∶3.5（volume ratio）］as test material，a greenhouse experiment was conducted to study the the amount of azotobacters and physicochemical properties in different water and nitrogen supply.Three water regimes（W1:80% of field capacity，W2:60% of field capacity，W3:40% of field capacity）and four nitrogen(N）practices（F0:0 kg·hm-2，F1:1 387.26 kg·hm-2，F2:924.84 kg·hm-2，F3:462.42 kg·hm-2）were designed.The results showed that the aerobic azotobacters’ amount were the highest in W2F2.The amount of nitrogen and irrigation waters irrationality was not beneficial to its amounts’ fecundity.And anaerobic azotobactors’ amount and pH increased with the increase of irrigation amount，but ammonium nitrogen and nitrate nitrogen content decreased.Effect was irregular to anaerobic azotobactors’ amount in nitrogen application，while ammonium nitrogen and organic matter content increased with nitrogen application increase.Nitrate content increased in the earlystage growth，in the later growth stage it did not change significantly.The increase of nitrogen reduced pH of the substrate，but too much nitrogen amount increased EC of substrate.In the condition of W1 and W2，EC increased with the increase of nitrogen.From the seedling stage to the fruiting early stage，the content of organic matter were higher in W2.When the irrigation amount was too high or too low，the organic matter content was difficult to increase.The organic matter content decreased with the increase of irrigation amount from the overwintering period to the fruiting later stage.Aerobic azotobacters had extremely significant positive correlations with EC and organic matter，and had significant positive correlations with ammonium nitrogen and nitrate nitrogen.It had extremely significant negative correlations with pH.The anaerobic azotobacters had extremely significant positive correlation with pH，and extremely significant negative correlation with ammonium nitrogen，nitrate nitrogen and organic matter.It was not related to the EC.The treatment 60% substrate relative moisture content+N 924.84 kg·hm-2 had the highest azotobacters’ amount and the best of the physicochemical properties.So the growth environment of the pepper under this treatment was optimal，and the cultivation of the pepper was most suitable in greenhouse. Key words：water and nitrogen supply；azotobacters；substrate physicochemical properties；correlation analysisdoi：1011838/sfsc.20170612