Focusing and imaging through scattering medium based on the optical transmission matrix is a hot topic in the field of optics recently. To measure the optical transmission matrix of the scattering medium and study special properties of the scattering medium, we propose a method named three steps phase shift interferometry to measure the optical transmission matrix of the frosted glass, and analyze eigenvalue distribution characteristics of the optical transmission matrix in Hadamard basis and Cartesian basis. Then combining the optical transmission matrix in Cartesian basis and phase conjugation, we achieve single point and multipoint focusing through scattering medium to verify the controllability of focusing points of the scattering medium. We study properties focusing through scattering medium with the camera in different positions, and measure the depth of focus of the optical system. We verify the lenslike effect of the frosted glass based on the controllability of the focusing points and the depth of focus of the system. The results show that three steps phase shift interferometry has the advantages of less measuring time and high enhancement factors of focusing; The eigenvalue distribution characteristics of the optical transmission matrix in Hadamard basis and Cartesian basis are both following the Gaussian distribution, which agrees well with theoretical prediction, and the correctness of the three steps phase shift interferometry to measure the optical transmission matrix of scattering media is verified; the focusable depth of focus of the system is long, within which the single point and multipoint focusing can be achieved.