The geology condition of Xiang jiaba hydraulic power station underground workshop is very complicated. Characteristics of crane beam of rock wall construction embodied in width of rock bench, huge bearing load, high quality requirements, urgent construction period and so on. According to inherent conception of “precision blasting”, technological measures of optimized excavation sequence, steel tube frame for drilling, double smooth blasting, equal and minim explosive and plum blossom shaped holes were adopted in construction. Through which, precision control of explosive energy release and rock fragmentation were achieved, insured the blasting excavation quality. Half-hole rate in Ⅱ surrounding rock was 100%, in Ⅲ surrounding rock was 99.2%, in Ⅳsurrounding rock was 90~97.3%, the phenomenon of under break was avoided absolutely, the average over break value was only 2.9cm, the non-smoothness is 0~4cm, the influence depth because of blasting excavation unloading was 0.2~0.7cm, the excavation effect was nearly perfect.