The gate assignment problem is the core problem in airport operation management. Existing studies more focus on the improvement of gate utilization efficiency and ignore the apron operation safety. To solve the problem， we propose a gate assignment model considering harbor safety constraints， aiming at maximizing contact gate utilization and minimizing loss of robustness. A branch and price algorithm is proposed to accurately solve the model. Actual airport data are used to verify the proposed model and algorithm. The experimental results show that， in the small-， medium- and large-scaled cases， the optimal value of branch and price is improved by 0.3%， 17.3% and 26.7%， compared with those of CPLEX， respectively， which has obvious advantages in medium- and large-scaled cases. The design can avoid harbor conflicts of 27.16%， 16.35% and 11.01% aircraft in small-， medium- and large-scale cases in advance， respectively. The safety of the apron is improved as well as the utilization rate of the contact gate and the robustness of the assignment plan.