The HgCdTe is a narrow band gap semiconductor. As the operating temperature increases， the intrinsic carrier concentration of the material will increase， the detector cut-off wavelength will become shorter， and the dark current will increase， which will cause the performance of the detector to decrease. HgCdTe infrared detectors usually work near 77 K temperature and obtain good detection performance， but low temperature operation will increase the preparation cost， power consumption， volume and weight of the detector. In order to solve these problems， under the premise of ensuring the normal working performance of the detector， increasing the operating temperature of the detector is an important research direction of the HgCdTe infrared detector. The p-on-n structure HgCdTe infrared focal plane detectors has the characteristics of low dark current and long minority carrier life， which is conducive to obtaining better detector performance under high operating temperature conditions. The performance of the p-on-n long-wave focal plane detectors is tested and analyzed at different operating temperatures. At 110 K， the noise equivalent temperature difference （NETD） of the p-on-n long-wave HgCdTe infrared focal plane detectors is 25.3 mK， and the operability is 99.48%， have better working performance under high temperature conditions.