Abstract: To solve the problem of long downtime and high cost of automatic production line, group maintenance model is put forward.Firstly, the target function is given, which describes the relation between inspection cycle and total downtime.Secondly, according to the delay time maintenance theory and the idea of group maintenance, namely reducing the total downtime by the means of batch maintenance, group maintenance model is established.Using data such as failure number occurred in production line, and the number of defects identified in PM, the established model can calculate the reasonable inspection cycle.Only with the calculated inspection cycle, the maintenance plan can be outlined, and the target of reducing total downtime by the means of maintenance batch will be realized.Finally, a case study is given.Failur es record data in the past decade are collected.Some advices are presented, which is based on the analysis of production flow, equipmentlay out, and the effect of equipments downtime as well.

Key words: automatic production line, group maintenance, delay time, inspection cycle