The invention discloses an electric composite supercharging variable compression ratio gasoline engine system. The system comprises main functional parts of an air inlet pipeline, a bypass valve, an electric supercharger, an intercooler, a variable valve timing mechanism, a variable valve lift mechanism, an engine body, an exhaust pipeline and a turbocharger. According to the system, the gasoline engine adopts large-geometrical compression ratio structure design and operates in a natural air suction large-compression ratio manner under medium and small load working conditions, so that the fuel consumption rate under the medium and small load working conditions is increased; under a large load working condition, lift of an intake valve is decreased, the closing time of the intake valve is advanced, and the gasoline engine operates in a small-compression ratio manner; composite supercharging of electric supercharging and exhaust turbine supercharging is utilized, so that the quick-response high-ratio supercharging capacity is achieved, and when the flow capacity of the intake valve is reduced, the requirement of the large load working condition on the inlet charge is met through high-ratio supercharging; and inhibition for knocking combustion of the gasoline engine under the large load working condition is facilitated through a small-compression ratio and high-ratio supercharging intake throttling refrigeration effect.