High accurate state of polarization (SOP) converting, low cost, low insert loss, and simple control algorithms are vital for polarization transformers. A novel method of polarization transformations using two quarter wave plates (QWP) and a half wave plate (HWP) realizing transformation between arbitrary states of polarization (SOP) is presented in this work. A new geometry method, SOP projection plane, is developed from Poincaré sphere method. The expressions of azimuths of three wave plates are derived through SOP projection plane method in Stokes space. The experimental results show that