Injection ratio control system for internal combustion engine

An injection ratio control system for an internal combustion engine (1) performs a multi-injection, in which multiple pilot injections and a main injection are performed. The system prohibits a first injection among the pilot injections if a main injection quantity command value for the main injection is less than an N time(s) minimum guarantee determination value. An injection quantity for the first injection is added to the injection quantity for the main injection. Thus, the system controls an injection frequency per combustion in the multi-injection to prevent the use of a minute main injection quantity command value equal to or less than the N time(s) minimum guarantee determination value. As a result, the main injection is prevented from vanishing.