In concrete construction, particularly large concrete pouring process, cracking is a common problem, so it is very important to seek a way of reducing and avoiding the cracks, so as to reduce the bad effect of cracks on the project quality. Combining the actual case, this paper carried out a comprehensive analysis of the causes of cracks on the bevel edge of chamber wall of the third-line Shaobo lock, and put forward the preventive measures from the design, purchase and use of materials and construction technology, etc., which have been proved feasible by the practice.