The invention relates to an assembly type recyclable deep foundation pit supporting system and a construction method thereof. The construction method comprises the following steps: enabling a row of vertical holes to be formed in the ground, and placing a vertical supporting body in each of the vertical holes to form a plurality of vertical supporting bodies; performing the first step earth excavation, enabling first anchor bolt holes or anchor cable holes to be formed in the inner sides of the foundation pit, placing anchor bolts or anchor cables, and performing cement grouting; enabling second anchor bolt holes or anchor cable holes to be formed, placing anchor bolts or anchor cables, and performing cement grouting; mounting first transverse support beams, applying a prestressing force, mounting second transverse support beams, and applying a prestressing force; mounting a first layer of vertical baffles between the first and second transverse support beams, and applying a prestressing force; repeating the steps to form the plurality of transverse support beams; and performing backfilling on the foundation pit and dismantling. The invention further provides the assembly type recyclable deep foundation pit supporting system which has the benefits as follows: the construction is simple, convenient, quick, safe and reliable, the materials can be used repeatedly and can completely replace conventionally used disposable piles, a large amount of steel bars and concrete are saved, and the problem that the materials in the conventional deep foundation pit supporting system cannot be recycled is solved.