Putra Mandiri Computer Pati shop which is engaged in the sale of computer accessories and peripherals still has problems in marketing, namely sales are still very limited, this is because the service is still using local sales methods, distributing brochures. The author is interested in conducting research to assist in helping to increase sales turnover at Putra Mandiri Pati by developing an online sales system. The development model used is research and development (Research and Development / R&D) and in the development of application software using the PHP programming language and database using My SQL. The results obtained in the form of a web-based sales information system that can be accessed online by the wider community and can serve online sales transactions and have been able to help increase sales turnover at the Putra Mandiri Pati Store.