Abstract: Quality and reliability of geodetic data depend on the size of its uncertainty. In this paper, uncertainty in measurement data is effectivey evaluated based on the theory of measurement uncertainty and fuzzy mathematics, A Function model using measurement uncertainty as unknown parameter is established to directly evaluate the uncertainty of survey data. The Fuzzy Entropy Measure is proposed as the optimal criterion to solve the function model. A corresponding algorithm is established; Experiemental results and comparisons with the least squares estimation show that the proposed method using a elevation monitoring network data solver is feasible.