Surabaya health service hospital uses the Medical Management System (M applications). However, the application is rarely evaluated. Inputs or feedback obtained from user cases, especially This study, is written to report the improvement of the SIMRS application model based on a heuristic assessment method. The method used in this study was to distribute questionnaires to the research objects that were evaluated, calculate the results of the heuristic assessment using the severity rating method, and then improve the model using the usability theory. This research consists of five usability components that demand improvement: visibility of system status, a match between the system and the real world, user control and freedom, error prevention, and recognition rather than recall. The conclusion is that five usability aspects have been fixed by following the concepts in the heuristic evaluation theory developed in designing a user interface model for the SIMRS application. This research employed a heuristic evaluation approach, which could determine the number of usability problems to be repaired. From the research, the level of problems in the SIMRS application user interface was minor problems. These problem solutions were given low priority in a SIMRS application model adapted to the usability principle.