As one of the pilot experiments of LHAASO, a hybrid array (HA) covering an area of ${20000 m^{2}}$ was successfully constructed by the end of ${2016}$ at the international Cosmic Ray Observatory at YangBajing (YBJ) in Tibet of China. This array consists of 115 scintillation detectors and 16 underground muon detectors of ${900 m^{2}}$. Using muons information, most of hadronic air showers are rejected at several dozens of TeV energy regime. With the data collected from ${2017}$ to ${2018}$, this work presents preliminary results on diffuse $\gamma$-ray emission from galactic plane. As a result, there has no significant excess of TeV $\gamma$-ray in the galactic plane with the YBJ-HA observation. Therefore, we put a 90% CL upper limit. We foresee that the under-construction LHAASO will have great potential in observing $\gamma$-rays in several dozens of even up to hundreds of TeV energy range.