Abstract: Laser tracker is the primary instrument used for carrying out three-dimensional position measurement in accelerator alignment. Theoretically, three-dimensional measuring data processed by three-dimensional adjustment is more rigorous, however, error accumulation is found in practice, especially in elevation direction, the error accumulation is very obvious. To control the elevation error accumulation of three-dimensional adjustment, a method using the geoid as a datum in the measurement and data processing is researched. The principle is to get the elevation measuring data based on the geoid and use the elevation data to construct the constraints equation then carry out the three-dimensional adjustment with elevation constraints. Take the laser tracker as an example, a three-dimensional adjustment function model is given, the construction method of the constraints equation is researched and the calculation formulas of the three-dimensional adjustment is derived. Two application methods of the three-dimensional adjustment function model with elevation constraints are studied and the effects in controlling the elevation error accumulation are showed by simulations. Finally, a group of measuring data are calculated and compared with various adjustment methods, the results show that the three-dimensional adjustment with elevation constraints can control the elevation error accumulation more effectively than the one without elevation constraints.