A sensitive micro-Pirani vacuum sensor has been fabricated. With effective schemes of ambient-temperature compensation and stabilization, it is capable of measuring vacuum pressure linearly from 1 torr down to 10-7 torr, a three orders-of-magnitude improvement in resolution over conventional gauges. A special electrothermal SPICE model, complementary to the conventional analog representation of thermal parameters, is also proposed. It allows a high-level sensor-circuit integrated simulation based on the most fundamental principle and thermal variables. Good agreement between the measured data obtained from a constant-temperature readout circuit and the simulation result is demonstrated.