The invention discloses a concrete plastic above water platform and an assembling method thereof. The concrete plastic above water platform comprises a plurality of platform units which are longitudinally spliced, the platform units are connected with one another through first connecting devices, each platform unit comprises a plurality of concrete plastic buoyancy tanks which are longitudinally spliced, the concrete plastic buoyancy tanks are connected with one another through second connecting devices, and the concrete plastic buoyancy tanks comprise plastic tank bodies; the interiors of theplastic tank bodies are filled with rigid foam, a walking platform is arranged at the tops of the tank bodies, and a longitudinal orbital groove dividing the walking platform into two symmetrical filling spaces is formed in the middle of the walking platform; and a plurality of parallelly formed grooves are formed in the bottom of each filling space, hollow rods are arranged in the grooves, and concrete layers are poured into the filling spaces. According to the concrete plastic above water platform and the assembling method thereof, the integral structure is simple and practical, the corrosion resistance is good, the water volatility resistance is good, dismounting and mounting are convenient, and maintenance is convenient.