Abstract: The commonly-used GPS cycle-slip detecting observations are used to detect cycle slips by wavelet method.The minimum cycle slips that can be detected by wavelet transform are obtained,and the wavelet method is compared with high order time differences.Double-difference phase data of cycle slip occurring twice in short time is calculated.Results prove that wavelet method works also well.A method about how to repair cycle slips based on wavelet transform is presented.Then tests are carried out.Results indicate that the method is feasible.