This paper proposes the automatic design method of comparator circuit by combination of game tree search and partial optimization. Because game tree search can remove redundant calculation, simulation time can be reduced. Using partial optimization can confirm the convergence of the optimize function of HSPICE. Thus, the proposed automatic designed circuit can satisfy the required specific. Compared with conventional method [1], we have succeeded in designing the comparator circuit whose design time is 3.3 times faster than the conventional one. Moreover, the automatic designed comparator satisfies all of the specific requirements.