A control system of a compression-ignition engine is provided, which includes an engine configured to cause combustion of a mixture gas inside the combustion chamber, an injector attached to the engine and configured to inject fuel into the combustion chamber, a spark plug disposed to be oriented into the combustion chamber and configured to ignite the mixture gas inside the combustion chamber, and a controller connected to the injector and the spark plug and configured to operate the engine by outputting a control signal to the injector and the spark plug, respectively. After the spark plug ignites the mixture gas to start combustion, unburned mixture gas combusts by self-ignition. The controller outputs the control signal to the injector so that a fuel injection timing is advanced when the engine operates at a high speed than at a low speed.