The invention discloses a deck laying composite waterproof structure and a construction process of the deck laying composite waterproof structure. The deck laying composite waterproof structure comprises a guardrail, a modified asphalt waterproof layer, a waterproof bonding layer, a deck plate and a laying lower surface layer, wherein the guardrail is vertically arranged on the upper surface of the deck plate; the inner side surface, near the deck plate, of the guardrail is provided with the modified asphalt waterproof layer; the waterproof bonding layer is arranged on the upper surface of the deck plate; the upper surface of the waterproof bonding layer is provided with the laying lower surface layer; and the height of the modified asphalt waterproof layer is greater than the thickness of the laying lower surface layer. Through the optimization of the deck waterproof structure, a gap between the deck laying layer and the guardrail is reduced; the erosion of the structure layer and the guardrail due to rainwater seepage is avoided; the durability of the deck laying layer is improved; in the construction process, the open flame hot melting in a conventional construction method can be omitted; and the goal of safe, convenient and fast construction is achieved. The integral construction operation is simple; the price is moderate; materials of the deck laying layer and the guardrail are enabled not to be corroded by the rainwater; and the maintenance and the construction in a later period are convenient.