Electrical calibration can be used to get the amplitude response of the seismometer. Among seismometers used in China, the most widely used electrical calibration method is sine calibration. But sine calibration has two problems in application：only part of the response signal can be used for analysis and it is not easy to implement the function of automatic data processing with the software. In order to solve the problems above，we introduce a new calibration method called overlapped sine calibration. In the test of the seismometer with this method，the response signal is continuous，and the transient response is only at the beginning of the whole response signal. Thus almost the entire response signal can be used to analyze. When processing the data, we only need to avoid the transient response at the beginning of the whole response signal. Therefore，it is easy to implement the function of automatic data processing with the software. This paper introduces the basic theory，the experimental procedure and the data processing method of the overlapped sine calibration. We also introduce an experiment using this method to test the seismometer. From the experiment，we find that the relative error of this method is less than 1%.