Range deterioration of Battery Electric Vehicle (BEV) under extreme environment temperature, especially under sub-zero temperature, has become one of the biggest challenges for Original Equipment Manufacturer (OEM). In this paper, a simulation model has been developed, which focuses on the correlation between range variation and environment condition. The concept of this model is to couple vehicle dynamics and the thermal behaviour of key components such as battery, electric drive system (EDS) and cabin. A matrix of steady-state experiments has been designed to calibrate this model. In conclusion, the confidence level in terms of relative error is within 2.2% for vehicle range, 2°C for battery temperature, 2°C for cabin temperature. After being validated, this model has been adopted to investigate the integrated thermal management system (TMS) of an A class sedan. A combination between thermal management of vehicle subsystems like battery, EDS and cabin has been explored in order to achieve a potentially maximum gain in terms of vehicle range. A potential 10.6% improvement of range under -7°C could be achieved. A map of range variation under different environment temperature has been drawn, indicating that the range variation was from 28.1% to 50.9%.