By an analysis of some characteristics of the environment physical field of a typical MCC,an important aspect of the environment conditions of the emergence and development of the MCC over the northwest of Shandong Province was revealed.The results show that MCC appears in the air layers of deep and thick high-energy-scale,quasi saturation and latent instability in the northwestern side of the subtropical high,and the middle-latitude short wave trough of 500hPa moving eastward is the initiation system of MCC.The conver-gence stream field of the upper-level jet stream and low-level jet stream play an important part in the emergence and development of the MCC.