At present, every manufacturer of intensity modulated radiation therapy (IMRT) equipment uses multi-leaf collimators (MLCs); however, each company’s intensity modulation methods and dose calculation algorithms differ. This study used four typical radiation treatment planning systems (RTPSs) employed domestically for prostate IMRT plans to carry out 15 case studies by one planner based on the dose limits at this clinic. The results were used to compare the differences, if any, in RTPS treatment plans. With prostate IMRT plans, an overlap area exists between the PTV and the rectum. For this reason, while observing dose limits of 60–75 Gy (within the dose tolerated by the rectum), securing uniformity and concentration of dose is essential to create the most appropriate treatment plan for the PTV and other targets. Although each RTPS uses different planning methods, it was generally possible to observe this clinic’s dose limits by adjusting the parameter values. When identical beam data is used, it is possible to create similar treatment plans.