Scattered light will cause the loss of system, damage the imaging quality of optical system and cause other hazards. According to the impact of scattered light of high reflective mirror in the optical system, the total integrated scattering method is put forward for measuring the total integrated scattering optic to get the ratio of the scattered light to the total reflected light. This method applies the theory of the total integrated scattered, considering about the photometric characteristic of integrating sphere. According to the principle of the method, a set of scatterometer is built, and the scattering of high reflective mirror is measured. After experimental verification, the result obtained by this scatterometer is very close to the consequence obtained by the scatterometer produced by Germany Laser Zentrum Hannover e.v. The values of Total Integrated Scattering (TIS) are both between 300 ppm and 500 ppm, which proves the feasibility of the self-made device.