An effective method for measuring high reflectivity (HR) of laser mirrors and high transmissivity of optical components with antireflective (AR) coats is described in this paper. The features of the method are that n-components with HR or AR ooats are measured at same time, and the measuring error is 1/n of the normal way. Measurements of a group of laser mirrors with HR coats and a group of thin disk with AR coats show the acceptability of the method.