A detection circuit and a detection method for liquid crystal display are provided. The detection circuit comprises a gate driver for providing row scan signal to liquid crystal cell to be detected; a signal source for providing polarity inversion signal to source driver; a 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. The polarity inversion signal comprises column polarity inversion signals each of which polarity inversion signal is continuous high level signal or continuous low level signal. The polarity inversion mode is a column inversion, which 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.