It is important to accurately previse the circumstances of the tunnel face in advance to realize a safe construction, because of the polytrope and indefinability to mountain ridge tunnel surrounding rock. However, it is also painful evaluating the detecting zone precisely because of the influence of complex geological conditions and uncertain interpreting outcome. With the study and application on long distance lead forecast in Sheng Ren Moutain tunnel of Mei Zhou-Da Pu highway using TSP48, this paper introduces the principle of parameters electing in data managing and detecting to achieve precisely explaining about the detecting zone. The interpretation is not only more close to practice, but also can provide a piece of reliable data to the construction, which can effectively promote the construction safe.