A kind of selective current limiting and capacity reduction operation method of shunt active power filter is proposed in order to improve the working reliability of active power filter（APF）. In case of insufficient capacity of APF inverter

the method is not simple to limit the compensation current

but to choose the compensation target flexibly and reasonable trade-off in accordance with the actual situation. On the basis of specified sub-harmonic detection algorithm

the harmonics containing less than 1% are eliminated firstly and the priority and harmonic compensation coefficient δnare set. The harmonics with the lower priority are eliminated gradually through the constant step decreasing of δnuntil the reference current value is lower than the maximum allowable value. The effectiveness of the method is proved by simulation and experimental results.