A new approach of detecting the black hole spin in x-ray binaries is proposed based on the model of the coexistence of the Blandford-Znajek (BZ) and magnetic coupling (MC) processes, in which the BZ process is used to power the jet emissions from x-ray binaries, and high frequency quasi-periodic oscillations (QPOs) are explained by a rotating hotspot in the inner region of the accretion disc surrounding a fast-spinning black hole. It is shown that the black hole spins of several x-ray binaries (XTE J1550-564, GRO J1665-40 and GRS 1915+105) can be constrained in a rather narrow range, provided that QPOs and jets coexist in these sources.