The moment estimates and maximum likelihood estimates of the truncation points in the truncated normal distribution are given, as well as the interval estimates for large samples. The estimation method of truncation point is applied to the assembly of DNA sequencing data, and moment estimation, maximum likelihood estimation and interval estimation of gap length are obtained. Monte Carlo simulations show that the experimental results are very close to the theoretical estimates. When the estimation method given in this paper is applied to a real DNA sequencing dataset, ideal estimation results are also obtained.