3.6MW series wind turbine gearbox is designed of planets + parallel shaft gearing structure, using power split arrangement and flexible pin technology, thus making gearbox compact in structure, high in reliability, duration in service life; applying gears made of quality alloy steel, in which external gears reaching class 5 (ISO1328) in precision and internal gears class 6 (ISO1328); carrying out dynamic simulation analysis with on gears with simulation software to get best profile effect; conducting FEM analysis on housing, torsion arm, planet carrier to optimize the structure under the precondition of ensuring strength and stiffness; providing forced lubrication to gears and bearings to ensuring gearbox service life.