In order to eliminate the Gibbs phenomenon existing in the boundary point or discontinuity in the process of timefrequency domain conversion and improve the accuracy of the data after transformation, a method for pulse extraction, which uses rootraised cosine function during extracting pulse, for the rolling oscillation error because of the boundary or break point introduced by rectangle window at time domain,is introduced, by analyzing the causes of the Gibbs phenomenon in the process of timefrequency domain conversion rolling oscillation error in the process of rectangle window extraction. In order to restrain Rolling oscillation error, an advanced method, which is rootraised cosine Kaiser extraction, is proposed. It could be found that the Gibbs phenomenon is eliminated by the rootraised cosine Kaiser extraction through MATLAB simulation and comparison of the data.The effectiveness is proved by the simulated result at last.