As the span of the suspension bridge increases, the height of the main tower and the force on the tower increase. The beam profile volume and pouring weight become larger, which increases the risk of high-altitude construction of the main tower and the upper cross beam. The main bridge of Wufengshan Changjiang River Bridge of Lianzhen Railway is the first rail-cum-road suspension bridge in China. The main span reaches 1092m and the total height of the tower is 191.5m. Taking the engineering practice of the upper cross beam of the main tower of Wufengshan Changjiang River Bridge of Lianzhen Railway as an example, this paper introduces the construction difficulties of the upper cross beam of the main tower, the selection of the upper cross beam construction support, the structural characteristics of the support and the construction process. The upper cross beam is constructed asynchronously with the tower. From the bottom of the upper cross beam to the top of the lower cross beam is 121.5m. The upper cross beam was poured in six times with a total concrete volume of 1918m3. The method of small trusses with bracket and floor steel pipe support is used for construction. The finite element analysis software is used to calculate the super-high support of the upper cross beam, and the support strength, rigidity and stability meet the requirements of the specification. At present, the bridge has been partially put into use, which verifies the rationality of the design and construction of the beam support on the main tower. It has strong reference and guiding value.