To interfere with an infrared focal plane array (IRFPA) detector effectively, it is necessary to analyze the response of the device under the irradiation of different wavelength lasers. Four lasers with different wavelengths are used in an irradiation experiment. The experimental result shows that the detection elements in the device can reach their saturation states easily and the device's response is in agreement with its spectral response curve. This has verified the relationship between the interference effect and the spectral response curve and provided the experimental basis for the middle infrared laser interference. Finally, the response mechanism of the infrared focal plane device to the laser irradiation in a given waveband is analyzed in brief.