The present invention discloses a method for measuring the concentration of a photoresist in a stripping liquid. In the method for measuring the concentration of a photoresist in a stripping liquid, a plurality of standard photoresist samples are prepared at first, then the spectrum of the standard photoresist samples and the spectrum of the test photoresist sample are collected, and the nth derivative of the spectrum of the standard photoresist samples and the spectrum of the test photoresist sample are taken, wherein n is an integer equal to or greater than 1, a standard curve based on the nth derivative curves and calculating the concentration of the test photoresist sample is established, the concentration of a photoresist in a stripping liquid can be measured accurately according to the standard curve.