A detection circuit and a detection method for liquid crystal display are provided. The detection circuit comprises gate driver for providing row scan signal to liquid crystal cell to be detected; signal source for providing polarity inversion signal to source driver, polarity inversion signal comprises continuous high level signal and continuous low level signal; source driver for performing digital-analog conversion on received display data signal according to preset reference voltage and polarity inversion signal, generating pixel voltage signal, and sending pixel voltage signal to liquid crystal cell to be detected, polarity inversion mode formed by pixel voltage signal is column inversion mode. The polarity inversion mode of column inversion, formed by pixel voltage signal in technical solution makes white dot of damaged area of alignment film is more prominent during detection process, so it would be easy for the operator to recognize it and avoid the issue of missing detection.