Environmental data synthesis method is one of the effective ways to solve small sample performance reliability estimation problem for complex electronic equipments. The most important part of this method is how to estimate the environmental factors. However, the existing estimation methods have the shortage of lower estimation precision and more difficulty in modeling. In view of these situations, an evaluation method for environmental factors based on circuit simulation was proposed. Firstly, the Pspice schematic of equipment (i.e. the physics modeling of equipment) was protracted. Then, the transient analysis, Monte-Carlo analysis and temperature analysis of Pspice software were used to attain the performance simulation data. Thirdly, environmental factors can be acquired for discretional environment situations by combining with the related theory of accelerated performance testing. Finally, an example of steady voltage power was provided and the validity and practicability of the proposed method were confirmed.