In order to evaluate the current safety status of the Maojiahe aqueduct, the finite element method is used to analyze the deformation and failure mechanism of the side wall of the aqueduct, and on-site inspection and safety evaluation of the foundation and masonry structure of the aqueduct are carried out. The results show that: (1) There is weathering and denudation on the surface of the masonry structure of the aqueduct, the masonry mortar is aging, the local cohesion is lost, the leakage of the aqueduct is serious, and the compressive strength of the mortar and the saturated compressive strength of the stone do not meet the requirements of the specification; (2) Affected by the water load in the aqueduct, the local tension occurs at the bottom of the inner side of the aqueduct overflow section, and the tensile stress range is 0 ~ 20 kPa, and the stress concentration phenomenon occurs at the bottom of the aqueduct; (3) The bottom of the side walls on both sides has shear failure, the left wall failure area has been penetrated, and the right side has not been penetrated yet; (4) The calculation results are basically consistent with the actual failure of the aqueduct, and the structure of the aqueduct is unstable. The results can provide a certain reference for safety reinforcement design of the later aqueduct.