Abstract: Prostate cancer is one of the most common malignant tumor for aged males in our country, radiation therapy is considered to be one of the best treatment. There is an increasing use of IMRT in the radiotherapeutic management of prostate cancer, which do target location by using imaging method. CT can not distinguish between prostate and its adjacent soft tissue structures very well, whereas, CT/MRI image fusion has an advantage of providing the internal structure of the prostate and estimating the tumor scale, with or without membrane damage and seminal vesicle invasion. So CT/MRI image fusion-based treatment planning allows more accurate target volume and risk organ, optimizes radiation therapy planning, protects adjacement organ and reduces radiation damage.