DArk Matter Particle Explorer (DAMPE) has a great potential in the search of monochromatic
and sharp gamma-ray structures in GeV−TeV range thanks to its good energy resolution. In this
work, we search for gamma-ray line structures using 5.0 years of DAMPE data. To improve the
sensitivity, we develop two types of data sets and adopt the signal-to-noise ratio optimized regions
of interest (ROIs) for different DM density profiles. No line signals or candidates, including
those located at 133 GeV and 43 GeV, are found between 10 GeV and 300 GeV in the Galaxy.
Therefore we calculate the 95% confidence level constraints on the velocity-averaged cross section
for 𝜒𝜒 → 𝛾𝛾 and the decay lifetime for 𝜒 → 𝛾𝜈 with systematic uncertainties included. Our
constraints on DM parameters are mostly comparable to the Fermi-LAT 5.8-yr results. The lower
limit for DM decay lifetime below 100 GeV are better than that of Fermi-LAT.