A simplified method for in-plane buckling analysis of pylons of multi-span suspension bridges was proposed. The analysis model is a pylon with an equivalent spring connected to it at the saddle. The stiffness of the equivalent spring was derived from the relation of the horizontal displacement at the saddle and restoring forces from the cables and was expressed with a simple formula. The stiffness of the deck is considered also in the simplified method. This method is suitable not only for three-pylon suspension bridges but also for the suspension bridge with multiple pylons. The example of the Taizhou Bridge with two span length of 2x1080m and three pylons indicates that the equivalent spring stiffness under different load case is not significant for a large span suspension bridge and the equivalent spring stiffness of mid-pylon is very small comparing with the side pylons, and the buckling problem of mid-pylons will be more important than side pylons for a continuous suspension bridge with multiple pylons.