A multispectral time delay integration (TDI) line array cooled infrared detector is developed. The detector array has a scale of 1024×4×6 and a pixel size of 20 μm×20 μm. The readout circuit has the function of serial output of analog signals that are converted into electrical signals through spectral segmentation, and integrating while reading (IWR), TDI, and blind/flash element elimination. The detector chip is made of HgCdTe epitaxial material to manufacture a photovoltaic diode array, packaged with a highly reliable all-metal vacuum dewar, and cooled using a small split Stirling refrigerator. The whole machine has advantages such as small size, low power consumption, wide response band, high integration, and short startup time. The test results show that the blind element rate of each spectral segment of the device is less than 1%, and the noise equivalent temperature difference (NETD) is less than 30 mK, the dynamic range of each spectral segment is greater than 70 dB, the non-uniformity of the response rate of each spectral segment is less than 5%, the nonlinearity of each spectral segment is less than 2%, and the device line frequency is greater than 20 kHz.