Air moisture in a greenhouse is an important factor to reduce crop diseases and insect pests and to increase crop yield. When soil moisture was 60%-70% of field capacity and the irrigating quota was 15mm, this paper experimentally studies the effect of air moisture on the growth of pepper in the greenhouse. Moreover, it analyzed the incidence of crop pests diseases respectively with small tube flow, infiltration irrigation, drip irrigation and furrow irrigation. The results show that the relevance between air moisture and irrigation methods is obvious. The variety trend of air temperature and air moisture are opposite, when the air temperature in a greenhouse is controlled between 25°C and 28°C, the air moisture in a greenhouse is lower. And the air moisture in a greenhouse is the lowest with infiltration irrigation, the incidence of crop diseases and insect pests is close to that with small tube flow and 35% lower than that with furrow irrigation; and the yield (2310kg/mu) is the highest with infiltration irrigation. The yield of pepper with drip irrigation, infiltration irrigation and small tube flow are 17%、39%、34% higher than that with furrow irrigation respectively.