Abstract: In the long-distance water transfer project with deep buried long tunnel sections, due to the influence of topographic and geological factors, it is difficult to arrange sensors in the whole line, and there are many "blind sections" that cannot be ignored in water transportation tunnels. The hydraulic safety monitoring range is small and difficult. Starting from the characteristic line method, this paper proposes a cross-time-step solution format for reconstructing the global flow field based on sensing data. The solution format uses the known data of the previous time step and the next time step to reconstruct the hydraulic parameters of the time step to be calculated. This paper verifies the feasibility and accuracy of the method through numerical simulation and experiments, and shows that the cross-time-step solution format can obtain important physical information from the sensing data, such as pipeline friction, hydraulic characteristics, etc., and reconstruct the flow field of the actual pipeline. The method has good anti-interference ability, and the sensitivity analysis of constant friction