Because of the constraints such as the information asymmetry, bounded rationality and so on in technology R&D alliances, the contract between the alliance members is not a complete contract and this kind of incomplete contract leads to the opportunism behaviors in the alliance members so that relational assets investment is reduced.This paper analyzes that the alliance members share the alliance interests by holding equities to form bilateral dependence relation in order to promote the incentive compatibility between the alliance members. By setting up the equity incentive mechanism model between an alliance leader and alliance members, the optimal relational assets investment and the optimal equity are obtained by solving the model. The effect of the relevant parameters on the relational assets investment and equity incentive is also analyzed, and finally, the related suggestions are given.