Abstract: Taking Sofradir 320×256 MW and 288×4 LW IR detectors as study objects was established a response model of MW/LW IR HgCdTe focal plane detector and calculated response characteristic curves of black body. Comparing the calculated curve of model with the test response of real detector output, at normal temperature range, it showed good agreement and indicated fine effect of the model. The model could provide meaningful reference for target detection with low temperature by FPA detector, in terms of the coherence between test results and simulative ones.