The invention belongs to the technical field of liquid leakage rate measurement in a nuclear island workshop of a nuclear power plant, and specifically relates to a device for measuring the liquid leakage rate in a nuclear island workshop of a nuclear power plant. The device comprises a cylindrical cylinder which is vertically arranged in a room floor (3) of the nuclear island workshop of the nuclear power plant, wherein the top end of the cylinder is connected with a drainage pipeline and groove (9) used for discharging a radioactive liquid, the bottom end of the cylinder is connected with aliquid discharging pipeline (7) provided with a liquid discharge control valve (6), the cylinder is internally provided with a liquid level meter probe (10) connected with a liquid level meter and timer (8), and the leakage rate of the radioactive liquid flowing into the cylinder can be calculated through the liquid level meter and timer (8). The setting of the leakage rate measuring device does not require an additional space, and only needs to replace the original floor drain. The device has the characteristics of small size, convenient replacement, easy implementation and simple structure,and the average leakage rate of the liquid in any time period can be calculated according to the liquid level information and corresponding timing information.