To be preemptive or waiting? The analysis on the entrance time of R&D project investment using option-game theory shows that the monopoly considers only the value of deferred investment. But there are two types of equilibriums for the duopoly, namely, the cooperative investment equilibrium which is invested later than that for the monopoly when the value of cooperation is always larger than that of preemption investment; and the leader-follower equilibrium when the two types of investment values have an intersection. Moreover, the critical point of investment is advanced because of the competition.