The close coordination between the number of line segments and the grid configuration，as one of the means of improving distribution network reliability，can significantly reduce the power outage time of users. Based on the research on reliability and economy parameters，a kind of high reliability segment rule is proposed with the grid economy and reliability considered together，and then a connection mode of short segments is presented. The result shows that，compared with domestic habitual segments（3 to 5），the number of segments has a substantial increase，so that the optimal segment number of an 10 kV line of 3～15 km is increased to 4 to 18 and the systems average interruption duration index with a tie-connection decreases from 3. 53～17. 63 h with no segments to 0. 67～2. 19 h with optimal segments，greatly improving the power supply reliability with the economic benefit guaranteed. Finally，a sensitivity analysis for the segment related parameters is performed. The outcome shows that the optimal segment number of a medium-voltage distribution line is greatly related to the price of a breaker/switch，the average planned outage rate，the energy loss cost and load distribution mode along the feeder.