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研究了SF6断路器操作过程冷态介质恢复特性，搭建126kV SF6断路器介质恢复特性试验回路，测量断路器不同开距下的击穿电压值。分析灭弧室充气压力、合闸速度、触头间电压极性对介质恢复特性和预击穿特性的影响，给出不同试验条件下的分闸介质强度恢复速度和预击穿时间。结果表明：断路器操作过程中相同开距下，合闸击穿电压值要大于分闸过程，断路器灭弧室结构下7mm开距内正、负极性下击穿电压值相差不大，极性效应不明显；开距大于7 mm，正极性击穿电压值大于负极性；合闸速度对合闸预击穿特性影响明显，合闸速度6.6 m/s的最大预击穿时间为1.18 ms，合闸速度4.7m/s的最大预击穿时间为2.21 ms，由此可知，提高合闸速度是控制预击穿时间的有效方法；针对126kV SF6断路器冷态开断过程，充气压力为0.7和0.5MPa时，分别在刚分时刻后0.5和1 ms内存在重击穿的可能，因此，针对容性小电流开断过程，应避免在此时间范围内熄弧。“,”Dielectric recovery characteristics during operation of high voltage SF6 circuit breakers were studied by tests. The test circuit of dynamic breakdown characteristics was built. Circuit breaker closing and opening dynamic breakdown voltage curves under the positive and negative polarities were obtained. Impacts of inflatable pressure and closing speed to dielectric recovery characteristics were analyzed. The breaking dielectric recovery rate and the closing pre-strike time under different experimental conditions were given. The results show that: the positive polarity breakdown voltage is greater than that of negative polarity of SF6 gas. The impact of closing speed on the closing pre-strike characteristic is significant. The maximum closing pre-strike time is 1.18ms under closing speed 6.6m/s. The maximum closing pre-strike time is 2.21ms under closing speed 4.7m/s. It can be seen, to improve the closing speed is an effective method to control the pre-strike time. Whenp=0.7MPa andp=0.5MPa respectively within 0.5ms and 1ms after contact separation, breakdown may occur again. Therefore, the arc should be avoided to extinguish in this time range.