  LHAASO is an instrument designed for detecting cosmic rays (CRs) and gamma
rays at TeV to PeV energies. The decays of heavy dark matter particles in the
Galactic halo may produce high-energy electrons that can be detected by LHAASO.
The main background for the LHAASO's CR electron measurements is the hadron
residuals due to mis-identification of the particle species. In this paper, we
estimate the LHAASO's electron background using the known all-particle CR
spectrum and the hadron rejection efficiency of LHAASO. With the estimated
background, we predict the capability of LHAASO to constrain DM decay lifetime
at 95% confidence level for various channels. We find that, if neglecting
systematic uncertainties, the CR electron measurement by LHAASO can improve the
current best results by up to on order of magnitude for DM masses between 100 -
1000TeV. However, indirect measurements of CR electrons by ground-based
experiments suffer from uncertainties included in the calculation, the
projected constraints will be largely weakened. So for using the CR electron
observation of LHAASO to constrain the DM parameters, the key point is whether
the systematic error can be effectively reduced.
