GNetAdj is based on the principles of indirect adjustment,and it is designed by Visual C++6.0.It can realize the adjustment and estimate of precision for level network,triangulation network,trilateration network,triangulateration network and other conventional control networks.Some methods of calculating approximation coordinates for special control network are discussed,and some methods of fixing the weight of different observations are analyzed.Finally,the program is verified by a case,and the result SHOWS that it has good practical value.