针对VBIC(vertical bipolar inter-company)模型对HBT多电压偏置下S参数拟合不够准确的问题,考虑了GaAs基HBT集电区载流子速度和耗尽层宽度随电压的变化关系,建立了随外加电压变化的集电区渡越时间方程.将得到的渡越时间方程内嵌到VBIC模型中,改进的模型提高了GaAs基HBT多电压偏置下S参数的拟合精度,其在很宽的电压范围内均与实际测试结果符合良好. Aiming at the problem that the VBIC (vertical bipolar inter-company) model is not accurate enough for the S-parameter fitting under the HBT multi-voltage bias, the relationship between the carrier velocity and the depletion layer width of the GaAs-based HBT collector with voltage is considered. The time-of-flight equation of the collector region changes with the applied voltage, the transit time equation is embedded in the VBIC model, and the improved model improves the fitting accuracy of the S parameter under the GaAs-based HBT multi-voltage biasing. Very wide voltage range are in good agreement with the actual test results.