Abstract: Patent licensing is the core of patent strategy, and the patent alliances are emerging more and more. The patent alliance member’s patent licensing investment strategy is studied. It is shown that the following aspects have clear influence on the alliance member’s optimal investment in licensing respectively: the effect of alliance member’s investment in licensing on the return increment of the alliance, on its return from other patents, on the return of other alliance members, and its share among the total alliance’s return. The substitutive effects of each member’s investment in licensing show no influence on the optimal investment.