The increase of distribution density of shared bicycles raises users’convenience on one hand，while worsens the conditions of public space on the other hand． As in many cities the public spaces are crowded with the shared bicycles and the pedestrians have been greatly affected． In order to optimize the distribution density of the shared bicycles and alleviate the disorderly occupancy of city’s public space，a sample city was surveyed on the users to determine the relationships between the distribution density and users’utility． Then，according to the pedestrian traffic flow characteristics and the evolution theory of crowded accident risk formation， the influence function of the drop density of shared bicycles on the reduction of public space， the comfort and safety of public space utilization was fitted． Finally，an optimization model of the distribution density of the shared bicycles in the case of paid occupancy of the public space was built to determine the distribution density according to the factors such as operators’profit，users’utility，public space occupation cost and the risk of safety accident of the pedestrians． The results of the case study show that by optimizing the density， the maximum number of bikers can be achieved， the pedestrian walking needs can be met，and the incidence of safety accidents can be reduced．