Cash is the most liquid current assets, often changes in every transaction, and it is required by every person. The internal effective cash control systems are very useful for management in providing reliable data and in making important decision in the company. PT Kereta Api Indonesia (Persero) is one of the SOE (State Owned Enterprises) that engaged in the transportation field. PT Kereta Api Indonesia (Persero) Regional Operations IV Semarang requires an effective internal control system in protecting cash and assuring the accuracy of accounting report on cash in the company. The types of the data that is used this research are quantitative and qualitative data. On the other hand, based on the research source, the writer also uses primary and secondary data. The writer uses observation, interviews, and library research in gathering the data. The method of analyzing is the descriptive qualitative method. The data shows that the internal control system of cash in PT Kereta Api Indonesia (Persero) Regional Operations IV Semarang has been operated well, because the company has fulfilled the elements of the existing internal control of cash, such as: the separation of functional duties, the explicit authorization system, periodic assessment of the physical cash reports by the internal audit cash reports, the evaluation of the employee who performed routinely. It was concluded that the internal control system of cash at PT Kereta Api Indonesia (Persero) Regional Operations IV Semarang is simple and good in its application.