Abstract: The effects of water deficit and deficit degree at different growing stages of cotton on yield and yield eomponents were studied by two years’pot experiments．The results show that the yield of cotton is improved when water deficit is imposed at seedling and boll opening stages，while the yield is significantly reduced by water deficit during the bud and flowering stages．The optimum water content levels are 50％ ～ 55％ of field capacityr at seedling stage，65％ ～ 70％ at bud stage．75％ at flowering stage and 50％ at boll opening stage of cotton．Ream nable control of the soil water contents can reduce the rate of bud and boll drop．