The genetic algorithm is used to synthesize the directional circular arc array as a sectored antenna. Then, the performance of this sectored antenna in indoor wireless millimeter wave channel is investigated. Based on the desired pattern and the topography of the antennas, the synthesis problem can be reformulated into an optimization problem and solved by the genetic algorithm. The genetic algorithm will always converge to global extreme instead of local extreme and achieves a good approximation to the desired pattern. Next, the impulse responses of the indoor channel for any transmitter-receiver location are computed by shooting and bouncing ray/image techniques. By using the impulse response of multipath channel, the performance of the sectored antenna on BPSK (binary phase shift keying) system with phase and timing recovery circuits is presented. Numerical results show that the synthesized sectored antenna is effective to combat the multipath fading and can increase the transmission rate of indoor millimeter wave system.