It researches the service efficient problem of logistics distribution center manual order picking, tour length and then. It builds picker route stochastic model under random storage S-type picking condition. It makes model approximation calculation with simulation result under order random arrival frequencies. It conducts well approximation between model and simulation results under the condition of permission error. It is the foundation for improving storage strategy. And it provides basic foundation for researching of picking time distribution function for manual order picking random service system.