In order to study the effect of low amplitude loading on residual stresses in cylindrical gear, the variety of residual stresses in the gear' root was investigated experimentally.The results show that residual stresses in cylindrical gear can't be relaxed under loads below fatigue limit.In the middle peri- od of fatigue life,the residual stresses can't be relaxed under loads close to fatigue limit,but be re- laxed under loads close to yield strength.