  Purpose: The High-Energy X-ray telescope (HE), one of the three main payloads
of the \textit{Insight}-HXMT mission, is composed of eighteen NaI(Tl)/CsI(Na)
phoswich detectors, where NaI(Tl) serves as the primary detector covering
20--250\,keV, and CsI(Na) is used as an active shield detector to suppress the
background of NaI(Tl) and also serves as an all-sky gamma-ray burst monitor
covering 0.2--3\,MeV. In this paper, we review the in-orbit performance of HE
in the first 5 years since \textit{Insight}-HXMT was launched on June 15, 2017.
Methods: The major performances we concern include the gain and energy
resolution of NaI(Tl) and CsI(Na) detectors, the performance of
pulse-shape-discriminator (PSD) and system dead-time. In this work, we
investigate these performances mainly using the data of blank-sky observations
and the data when the telescope in earth occultation. Results: The overall
performance of HE/NaI(Tl) is very stable in the first 5 years, whereas the gain
of HE/CsI(Na) shows a continuously increasing trend and should be calibrated
regularly. Conclusion: In general, HE is still in good health and
well-calibrated status after five-year's operation. The in-orbit performance of
HE has no significant deviation from expectation. HE is expected to be in
operation healthily for another several years of extended mission life.
