Taking the fourth Yuanshui Bridge in Changde as the construction background， the space finite ele- ment models of semi-floating system， pylon and girder rigid fixity system and rigid frame system were estab- lished respectively to investigate the serviceability of structural systems for multi-span-short tower cable-stayed bridges. The action effects under static and dynamic conditions were analyzed and compared. The results indi- cated that the distributions of load effects were fairly even under the static force and seismic action due to the structural stiffness of rigid frame system. But the internal forces in piers and towers of rigid frame system were strong with global temperature rising. There were relatively large deformations and small temperature internal forces of semi-floating system and pylon and girder rigid fixity system. And the response of each pier under braking force or seismic action was obviously different from the semi-floating system and pylon and girder rigid fixity system. The structural system of the Fourth Yuanshui Bridge is a combination of rigid frame system and pylon and girder rigid fixity system， which solves the excessive stress of the abutment pier under thermal action. Moreover， the fixed piers are divided into two adjacent legs to reduce the thrust rigidity of pier， which do not increase the foundation quantity and also achieve fine aesthetic effect.