In this paper, the scientific thinking, method and reason of the medium-and short-term earthquake prediction and the forecast on the spot before and after the Lancang earthquake with M=7.6 and the Gengma earthquake with M=7.2, which occurred on Nov. 6, 1988, have been objectively expounded. The main reason of the medium-term prediction includes the basic seismieity characteristics, the 47-year recurrence period of great earthquake and the accumulated strain energy. The main criteria of the short-term prediction embrace the dynamic deduction of seismicity centers in the southwestern Yunnan, the direction shifting track of epicenters of earthquakes with M ≥ 5.0 and the analysis of seismicity process. Σ√E-lgt and b-value intercept method is effective methods determining and predicting the largest aftershock on the spot, Finally, this paper sums up and reconsiders the prediction.