Abstract: Dose rate effects of SiGe heterojunction bipolar transistor (HBT) with different biases were studied. A three-dimensional numerical simulation model of SiGe HBT was established with Sentaurus TCAD software, and the changes of Gummel characteristics and transient current peaks of each terminal with time at different dose rates were simulated. The results show that transient current peaks of each terminal increase with dose rate. The worst biases for dose rate effect were different for different terminals. For the same terminal, the transient current peak is different, the transient current of collector is large under substrate reverse bias, the transient current of base is large under cut-off bias and transient current of substrate is large under substrate reverse bias. The main reason for the phenomena is that different biases affect the change of carrier transport mode and the applied electric field.