This paper uses the interval quadratic preference loss function to establish the threshold model of exchange rate volatility by Taylor series expansion, and GMM method to study the intervention behavior of exchange rate. It found that the central bank has asymmetric intervention preference for exchange rate, discontinuous and nonlinear intervention for exchange rate, and there is an intervention threshold, and the central bank has a certain degree of “fear of appreciation” trend. To some extent, asymmetric interval intervention preference has resulted in the rapid growth of China's foreign exchange reserves.