The invention discloses a modular construction method for a water distributing system in a cold storage tank. The method comprises the steps: gathering structural data of a water distributing member, arranging water distributing pipelines in a simulating manner, and setting a unique RIFD code for the water distributing member; constructing a water distributing member conveying device; erecting a water distributing system on the top of the tank; erecting a primary vertical tube in the tank; erecting a water distributing system in the bottom of the tank; and externally coating the water distributing system pipeline and the cold storage tank with insulating layers so as to realize modular water distributing construction. The mounting accuracy can be ensured by mounting at one time by integrating simulated distribution of an electronic terminal, radio frequency coding of unique identifier, special water distributing member conveying device and field construction and mounting, so that the time is shortened, the labor is saved, and the human cost is greatly lowered; by means of primary water distribution in double inner rings, distributive pressure equalizing secondary water distribution and third water distribution by a water distributing cap, the wall attachment effect is increased, fine and uniform flow water distribution is realized, the thickness of an inclined temperature coating in the tank is effectively maintained in an efficient level, and the cold storage effect is good.