  In this paper we proposed a joint reconstruction of \gray events using both
extensive air array (EAS) and Imaging air Cherenkov Telescope array (IACT). We
considered eight Cherenkov telescopes to be built on the LHAASO (Large High
Altitude Air Shower Observatory) site and investigate the improvement in
differential sensitivity when combining the information from both IACT and Moun
detectors of LHAASO-KM2A. We found that due to the higher cosmic ray background
rejection power and higher gamma ray retention ratio provided by muon detectors
of LHAASO, such a joint reconstruction can significantly improve the
sensitivity of IACTs, especially for extended sources and long exposure time.
In this article, we have shown the performance of an eight-telescopes mini
array, and our results indicate that above $10~\rm TeV$, the sensitivity can be
improved by muon detector from $25\% - 60\%$ in different energy ranges.
