Based on the data of quick access record(QAR), a mathematical model was formulated to find the high risk subspace-, which has high probability for a special QAR exceedance in landing stage, in the space- consisted of the flight operation indexes, such as decline rate, aircraft pitch, etc. Focusing on this QAR exceedance, data of above mentioned indexes at 20 feet radio altitude and their change ratios from 20 feet to 0 feet were considered in the method. Preliminary analysis shows that the QAR exceedance samples and the normal samples have a similar ratio in the scope with more than 62 tons total-landing-weight and less than 32 Celsius degrees landing-temperature. This result reflects that environmental factors in this scope may be not the main mechanism of this QAR exceedance. For elaborately diagnosing these samples, the objective of the mathematical model is maximum ratio of QAR exceedance; the subspace- must satisfy certain sample size. An algorithm based on golden section was provided, and threshold values of each index were found. The result would guide the pilot’s simulation pertinence training.