Through estimating the natural rate of interest in China, we provide a "benchmark" for measuring and describing the tight or easy monetary policies. The monetary policies are tight when the real rate of interest is higher than the natural rate of interest, and vice versa. In order to examine the asymmetric effects of monetary policies in China, we use the impulse-response function to simulate the dynamic response of GDP gap rate and inflation rate to the shock of tight or easy monetary policy. We find that the tight monetary policies have stronger output effects and weaker price effects than the easy ones. The analysis to the results implies that the gap between the real rate of interest and the natural rate of interest can not only reasonably measure the degree of tightness of the monetary policies, but also become an important reference of making or assessing the monetary policies.