A compression-ignition engine control system is provided, which includes an intake phase-variable mechanism and a controller. The controller controls the intake phase-variable mechanism to form a gas-fuel ratio (G/F) lean environment in which burnt gas remains inside a cylinder and an air-fuel ratio is near a stoichiometric air-fuel ratio, and controls the spark plug to spark-ignite the mixture gas to combust in a partial compression-ignition combustion. The controller controls the intake phase-variable mechanism to retard, as an engine speed increases at a constant engine load, an intake valve close timing on a retarding side of BDC of intake stroke and an intake valve open timing on an advancing side of TDC of exhaust stroke, and controls the intake phase-variable mechanism so that a change rate in the intake valve open timing according to the engine speed becomes larger in a high engine speed range.