The invention provides a method for erecting a deepwater steel trestle and a platform on exposed bedrock in the shallow sea. The method includes establishing a model, determining parameters, piling steel pile and forming the integral frame structure. The method is particularly applicable to engineering of steel trestles, platforms and docks and the like in the shallow sea and deep areas with exposed river-cross bedrock, is simple and fast in construction and can be finished and operated conveniently in a high construction quality and low cost manner by the aid of small-sized universal mechanical equipment. Besides, the method is not only applicable to areas with thicker coverage layer but seabed areas with thin coverage layer or without coverage layer, is high in applicability to construction sites and has evident social and economic benefits.