Abstract: Datum unification and coordinates transformation are always one of the key problem in surveying engineering project. In this paper, the results show that the barycentric coordinates method adopted to overcome the strong correlation problem between the parameters in coordinates transformation model, are basically the same as the four- parameter method. This method simplifies the calculation and enhances the reliability of numerical calculations. Due to the extensive application of modern computing devices, the difference between the two methods is not obvious. The reliability of various coordinate transformation algorithms depends heavily on the accuracy and the distribution of known points. In polar coordinates method, it is extremely significant to avoid short sides, which is remarkable difference with others, participation in parameter solution.