  Aims. We aim to investigate the molecular environment of the supernova
remnant (SNR) G150.3+4.5, and explore its association with ambient molecular
clouds (MCs). Methods. We present large-field CO (J=1-0) molecular line
observations toward SNR G150.3+4.5, using the 13.7 m millimeter telescope of
the Purple Mountain Observatory. The observations have an angular resolution of
$\sim 55 ''$. We analyzed the spatial distribution of MCs in relation to the
SNR shell detected in previous Urumqi $\lambda$ 6 cm radio observations and
examined the CO spectra for kinematics information. Results. We find that MCs
at the velocity range of [-14, -2] km s$^{-1}$ are spatially distributed along
the radio shell of the SNR. Line broadening and asymmetries are observed in the
CO spectra of the clouds. Moreover, we find that the molecular clouds around
the shell have systematic velocity gradients in the position-velocity (PV)
diagrams. Both morphology alignment and gas kinematics suggest that the SNR is
associated with the ambient MCs at $\sim$ 740 pc. Based on the CO gas distance,
the dimension and the age of the SNR is estimated to be 40 pc $\times$ 33 pc
and 3.8 $ \times 10^4$ years, respectively. The very high energy emission of
1LHAASO J0428+5531 toward the SNR may originate from the interaction between
the SNR and the surrounding MCs.
