An equivalent pixel circuit for 300×400 infrared focal plane array readout circuit structure is presented in this paper. The circuit′s electrical characteristics are equivalent to that of the vanadium oxide (VOx film) micro-mechanical systems (MEMS). It can simulate the variation of the branch current when the MEMS pixel changes. Before the growth of physical structure of MEMS (VOx film),the infrared array detector readout circuit has been fabricated. The equivalent pixel circuit is designed to test the electrical properties of the readout circuit. It can remove the defective products and reduce packaging costs. The circuit has been designed and fabricated with a GlobalFoundry 0.35 μm process. The test results indicate that the equivalent circuit has the same electrical properties as the MEMS pixel when the integrating current is 0~200 nA.