The wind turbine generator system utilizes environmental wind to produce electricity through wind-driven rotation of a turbine generator. The system includes a housing having upper and lower portions and a main open cover mounted thereon. The main open cover is configured to direct wind through an opening formed through the upper portion and into an interior thereof. A main turbine is rotatably mounted within the upper portion, with the environmental wind directed by the main open cover driving rotation thereof. The main turbine has a central aperture formed therethrough, with rotation of the main turbine driving air flow downwardly therethrough. A secondary turbine is rotatably mounted in the lower portion of the housing, with the secondary turbine being driven to rotate by the downwardly driven air generated by the main turbine. The secondary turbine partially drives rotation of the main turbine. An electrical generator is linked to the main turbine.