This paper studies on how members of alliance’s investment policies are influenced by R&D spillovers, control on own R&D spillovers and innovation ability, and determines the optimal allocation that the alliances obtain the maximum expected investment. This research shows following conclusions: 1) R&D spillovers and innovation ability have positive effects to increase members’ R&D investment, and control on own R&D spillovers has negative effects to members’ R&D investment, but its influence is weak. 2) The equal profit-sharing arrangement is the optimal profit-sharing arrangement to the alliances with strong innovation ability. For alliances with weak innovation ability, it should choose proportional profitsharing arrangement when market profits are low, and should choose equal profit-sharing arrangement when market gains are high.