In order to improve the operating speed of bus, the forecast system for passengers up and down buses (FS-PUDB) could be adopted to inform the bus drivers whether any passenger would get on or off at the next bus stop before stopping. When there is no passenger up and down, the bus can pass directly without stopping, increasing operating speed. Based on the stochastic theory, the paper gave the calculating methods for the probability of passengers up and down bus, and the operating efficiency under FS-PUDB. Monte Carlo simulation method was adopted to meet the system randomness. The example shows that, with the passenger flow 10 passengers per bus frequency with 6 staging stops, the operation efficiency of buses is to reduce the delay at bus stops 24.2s. The benefit is obvious. And the system efficiency presents declining curve by passengers flow, and would increase with the number increasing of bus stops, which provides the basis for the promotion application of FS-PUDB.