针对芜湖段实测的船舶交通流数据，由到船时间与船速计算船舶间距，分析不同船舶间距下船速的分布变化.结果表明，上行船舶间距为20~160 m，下行船舶间距为30~300 m时，船速服从对数正态分布；上行船舶间距为160~400 m，下行船舶间距为300~600 m时，船速服从正态分布.在速度变化临界点处，分析相邻两船速度差值变化，得到船舶最小安全间距：上行船舶最小安全间距为140~180 m，下行船舶最小安全间距为260~340 m.对所得船舶安全间距进行船舶交通流仿真，结果证明最小船舶安全间距范围有效.

According to vessel traffic data measured in Wuhu section, vessel clearance is calculated by the arriving time and vessel speed, and the speed distribution of different vessel clearance is analyzed. Results of speed distribution show that vessel speed obeys lognormal distribution when upstream vessel clearance ranges from 20-160 m and downstream vessel clearance ranges from 30-300 m, while the speed obeys normal distribution when upstream vessel clearance ranges from 160-400 m and downstream vessel clearance ranges from 300-600 m. The minimum safety clearance range is obtained on the critical point of the speed variation after analyzing the difference between the changes in the speed of the adjacent two vessels. The minimum safety distance of upstream ships ranged from 140-180 m and that of downstream vessels ranged from 260-340 m. Simulation for the safety clearance show the effectiveness of minimum safety clearance.