Abstract: Power Electronic Transformer (PET) is the key equipment of future AC/DC hybrid power distribution network. One of the key difficulties for efficient simulation of PET's multiple working conditions is equivalent modelling under blocking state. This paper put forward an equivalent modeling method suitable for the blocking state of cascaded H-bridge based PET (CHB-PET). First, a practical example was used to explain the circuit characteristics of the blocking state. After the simplification, the Thévenin-Norton equivalent parameters in the partially blocking and totally blocking states were derived. Then, three implementation methods of the blocking equivalent model were analyzed, and an integrated method of sharing the state variable storage unit with the non-blocked model is proposed. A typical 10 kV / 3 kV three-phase CHB-PET system was built in PSCAD / EMTDC, and the blocking conditions during startup process, AC voltage sag, and DC fault were simulated. The results show that compared with the detailed model, the blocking methods proposed in this paper have sufficient simulation accuracy. The work in this paper can also provide a reference for the blocking modeling of other modular converters containing multi-stage power transformation.