AC filters (ACFs) for different harmonics are installed in HVDC stations, they switch on and off very often with circuit breakers for reactive power compensation. ACF breakers bear transient recovery voltages (TRV) comprising AC and DC voltages after switching off large capacitive current, because the DC voltage component is decided and divided by resistance which is influenced by the ambient environment of porcelain breaker external insulation, the TRV may exceed the insulation requirement. Using a typical 550 kV AC filter procelain breaker with two breaks used in HVDC stations as an example, a simulation model of TRV is established based on PSCAD to simulate the influencing factors of TRV. The simulation results show that the ambient environment, such as humidity, dirt and dry zone, can seriously affect the TRV of breaks. With specific ambient environment conditions, when the break resistance decreases and the diffence between the two break resistances is large, the maximum break TRV may approach or even exceed the theshhold value, which will result in breaker restrike or flashover.