Asymmetry information between investors (principal) and manager (agent) always exists in the process of venture capital investment. The paper establishes an option game model from the view of investors in order to study the manager’s private benefits and designs an optimal contract for the entrance of venture capital. In the presence of principal-agent problem situation, the option’s executing time is bounded by the contract, so that the agent would not miss optimal entry time by advancing or delaying their investment. The principal must be paid to the agent as an incentive means.