The utility model discloses a fuel evaporative emission system for an internal combustion engine with a mechanical supercharger. The fuel evaporative emission system comprises a charcoal canister assembly, an electromagnetic valve connected with the charcoal canister assembly, and a first reverse check valve, wherein the charcoal canister assembly is used for collecting evaporated fuel vapor in a fuel system and sending the fuel vapor into the intake manifold of the internal combustion engine; and the first reverse check valve is arranged in a pipeline which connects the output end of the electromagnetic valve with the intake port of the intake manifold. On the basis of the prior charcoal canister flushing technique and through the structure improvement design, the fuel evaporative emission system can ensure the fuel vapor accumulated in a charcoal canister to be flushed out in time, thereby meeting the emission control requirement. An engine control unit (ECU) is used for monitoring the pressure in the input end of the mechanical supercharger, the intake manifold, the charcoal canister and the like so as to flush the charcoal canister in all conditions, thereby effectively raising the fuel utilization ratio, saving the energy consumption and reducing the environmental pollution.