In order to use the fiber strain measured by distributed optical fiber sensing technology to reconstruct the three-core optical fiber three-dimensional morphology,this paper designed a r econstruction algorithm and uses the finite element solution data to verify it.First,the calculation method of the curvature and the sampling value of the bending direction of the three-core fiber was designed.The curvature and torsi on continuous functions were constructed by the cubic spline interpolation method,and the space curve formul a under the arc length parameters was designed based on the Frenet-Serret framework.The three-core fiber finite element model was solved,and the fiber strain distribution data of unidirectional bending and S-shaped bending w ere solved and extracted,and then brought into the designed algorithm to solve the three-core fiber morphology re construction; finally through the mean square Root error and normalization accur acy are calculated and analyzed for reconstruction error.The results show that the error of the three-core fiber 3D shape reconstruction algorithm d esigned in this paper is controlled within 0.07%.The algorithm has good restoration effect,high precision,and has certain theoretical and engineering application value.