The invention discloses a differential serving as a power coupling device of a combined hybrid vehicle, and aims to solve the problem of sliding friction between a planet gear (3) and planet gear shafts (4). The differential comprises a differential shell (1), an axle shaft gear (2), the planet gear (3), the planet gear shafts (4), a bearing cap (5), rolling bearings (6) and a gasket (7), whereinone end of each planet gear shaft (4) is arranged in an axle hole of the planet gear (3); the planet gear shafts (4) are in interference fit with the axle hole of the planet gear (3); the other ends of the planet gear shafts (4) are arranged in upper and lower holes of the differential shell (1) through a pair of rolling bearings (6); rotation axes of two planet gear shafts (4) are collinear and are vertically crossed with the rotation axis of the axle shaft gear (2); the bearing cap (5) and the gasket (7) are fixed on the end faces of lug bosses at the outer ends of the upper and lower holesof the differential shell (1); and a gap is reserved between the back face of the planet gear (3) and the inner wall of the differential shell (1).