The real-time passenger flow of buses is a very important statistics for intelligent public traffic system. This paper proposes a real-time bus passenger flow statistics scheme based on light-sensitive wireless sensor network. We deploy five light-sensitive wireless sensor nodes at specific locations near the front and the rear doors. By utilizing the fact that the outputs of light-sensitive sensors are evidently correlative with the passengers passing through, a low complexity algorithm is designed to count the number of passengers up and down. The most remarkable superiority of the proposed scheme is the capability of accurately detecting the case of two passengers getting off the bus abreast. Moreover, the scheme costs low and there is no need to modify the internal circuit of the bus. The proposed real-time bus passenger flow statistics scheme has greatly extensive applications.