Abstract: This paper discusses cycle slip problem and its solving method in two different cases.In static case,a 4-order polynominal is produced using least square method,and it is used to predict the next epoch phase observable to find out cycle slip.In kinematic case,Kalman filter method is used to perform statistic test with phase residual,if dual phase observables are provided,the ionospheric residual is produced to perform two step cycle slip detection,thus to enhance its capability.All the above methods are verified with field phase data.