Abstract: Nanjing Third Yangzi River Bridge was the first cable stayed bridge in China. Its main tower was the form of steel structure. The key technology of the steelpylon’s process assembling was investigated to meet the characteristics of the steelpylon’s construction. The method of the control network’s building for assembling survey was introduced. The inner controlling method and the method combined inner controlling and outer controlling were pointed out. Quality evaluation was made for the assembling surveys’s result. The results showed that the survey methods could meet the requirement of design and construction. It could also be a reference for the similar steelpylon’s engineering projectors.