This paper analyzed the principle and the precision of trigonometric leveling with reciprocal observation,designed a tool to measure the instrument and target heights accurately.These have been applied to the height surveying in Daya Bay reactor neutrino experiment.With a large contrast of elevation difference between trigonometric and spirit leveling,it was finally approved that trigonometric leveling could reach the requirement of second-order leveling,and obtain the most favorite distance for the observa...