Eastern China is the globally unique land region with lots of middle stratiform clouds in cold seasons. The distribution of this specific stratiform cloud is determined by three main factors, viz, relative humidity, stable stratification, and ascending motions. The large relative humidity in cold seasons provides a basic moisture condition for clouds, the ascending motions generated by the convergence in the low atmosphere and divergence in the middle troposphere provide a favorable dynamical condition for middle clouds, and the midlatitude temperature inversion provides a favorable stable stratification for the stratiform clouds. In addition, the co-effects of the divergence in the low and middle atmosphere dominate the middle stratiform cloud amount over eastern China.