Abstract: The influence of adding amino acids on population growth of Tyrophagus putrescentiae and predatory function of Neoseiulus barkeri was investigated in laboratory. T. putrescentiae was reared using wheat bran amended with 1% amino acid at 25 ℃, RH 80% and photoperiod 16L:8D. Addition of four amino acids (valine, leucine, methionine and threonine) enhanced the reproductive capacity of T. putrescentiae, valine being the most effective amino acid. When 2000 T. putrescentiae were inoculated to 50 g mixed diet, population of T. putrescentiae reached as high as 15072.3±710.8. Predation of T. putrescentiae by N. barkeri was significantly increased by 76.96% in the rearing with addition of histidine compared with the control.