The errors of three dimentioned(3 D) profilometry based on quadrature demodulation are analyzed,and the corrected results are present.We found the method had three primary errors:the error that is caused by speckle of laser interference system,the error that is caused by mixing in quadrature demodulation,and the error that is caused by the cosine fringe distortion in the structure light.We analyzed these three errors by experiment and theory.At last,we gave the corrected results.