In the process of integration of processing and measurement, the optical on-machine measurement accuracy is seriously affected by the oil film formed by cutting fluid remaining on workpiece surface. The existing error compensation methods generally require the prior information of the oil film, such as composition, thickness, etc. Nevertheless, this information is hard to obtain in real time due to factors of processing and random distribution of cutting fluid. For these reasons, a displacement error compensation method for surfaces with cutting fluid adhesion based on multi wavelength laser is proposed in this article. First, a multi wavelength laser measurement system is designed and set up based on laser triangulation, which can measure the displacement of the same measured point by using multi wavelength laser. Then, the Cauchy dispersion law is introduced to establish the analytical relation between the optical system and the laser wavelength. Next, the inherent difference property of multi wavelength laser measurement is deduced, and the error compensation is realized. Experiments are performed according to the method in this article. The experimental results show that the absolute value of measurement error after compensation is less than 0. 01 mm. Compared with the uncompensated measurement data, the error is reduced by at least 92% .