Disclosed are a dual-trench low-on-resistance and low-gate-charge silicon carbide MOSFET device and a preparation method. The device comprises a source, a first conductive type source region contact part, a second conductive type base region, a heavily-doped second conductive type trench region, a first conductive type polysilicon gate, a second conductive type polysilicon gate, groove gate dielectric, a second conductive type gate oxide protection region, a first conductive type packaging region, a first conductive type drift region, a first conductive type substrate and a drain. By virtue ofa space charge region formed by the first conductive type polysilicon gate and the second conductive type polysilicon gate, coupling between the gate and the drain is lowered, thereby lowering gate charge of the device; by virtue of the first conductive type packaging region, the space charge region formed by the second conductive type gate oxide protection region in the drift region can be reduced; in addition, effective current transmission can be realized, so that the on resistance of the device can be lowered; and by virtue of the heavily-doped second conductive type trench region, the gate oxide electric field can be shielded effectively, and the gate oxide can be protected.