The construction of a modern long span rigid frame box girder bridge gives impetus to the development of structural analysis design theory and construction technology. Moreover, it makes construction monitoring of the rigid frame box bridge a significant research subject. Construction monitoring of the rigid frame box bridge signifies regulating the structure’s internal force and alignment in the construction process and completion state, and thence satisfies the designed expectation. Based on the construction monitoring of Liang-Ji Canal Bridge project, the construction process and the designed completion state have been simulated and analyzed at a certain precision level . A plane bar finite element computational model is established, and the alignment and internal force of the bridge in each construction stage are analyzed. Then the simulation analysis of construction process is derived according to its construction characteristics . Through systematical research on the form work elevation and the stress monitoring of the cantilevers during the cast-in-situ construction, the factors which influence deflection and stress are analyzed. The elevation is predicated by the Kalman's filter estimation, the modified grey model and the combination of these two methods. The stress monitoring error and corresponding reasons are analyzed. The measured results show that the combination of the two approaches can improve prediction accuracy. The presented analysis, processing and control methods accumulate many experiences for the design and construction of the long span box girder rigid frame bridge.