In this paper, we consider multiple primary and multiple secondary users cooperative cognitive radio networks, in which the primary users (PUs) lease a portion of their spectrum to the secondary users (SUs) for some revenue, and in return the SUs play as relays and help forward the data of the Pus in exchange for being granted spectrum opportunities. Both the PUs and SUs aim to maximize their own utilities. The spectrum leasing and relay selection problem is studied. We formulate the spectrum leasing problem as a Stackelberg game, and transform the relay selection problem as an assignment problem which is solved by the Hungarian method. Numerical results show that, under the proposed cooperative spectrum leasing-optimal-relay-selection scheme, both the primary and secondary network can achieve high utilities.