Abstract: In order to strengthen the protection of the surrounding building during the tunnel drilling and excavation process, a t-distribution charge optimization formula and a sensitive interval calculation model were established based on the principle of statistics in this paper. Meanwhile, based on the practice of drilling and blasting excavation in Guiyang Metro Line 2, taking the proportional charge as a variable, the variation tendency of the optimized charge in the t-distribution with the proportional dose and the charge control of the explosion source in the forward movement process were studied. The study results present following conclusions. Firstly, the confidence probability with the traditional safety charge prediction formula is only 50%, the confidence probability based on the t-distribution formula can reach 99%. It is known that the t-distribution charge optimization formula can increase the protection degree to the surrounding building. Secondly, when the proportional charge is between 0 and 0.053,the asymptote of the critical charge approaches 0, therefore, this proportional dose interval cannot be used to guide the blasting construction. When the proportional charge is more than 0.053, the vertical vibration velocity is the largest, so the optimization charge formula can be used to guide the blasting construction. Finally, in the tunnel excavation direction line, the safety control charge is a process of gradually decreasing-reaching the minimum-rapidly increasing. When the working face is in the sensitive area, it is necessary to adjust the blasting design project in time to strengthen the protection to the surrounding buildings.