The invention belongs to the technical field of heavy metal ion detection, and provides an apparatus for detecting mercury, lead and arsenic ions in a water body based on quantum dot resonance energytransfer of intelligent equipment and a method thereof, which can be used for solving the problems of complex detection apparatus for the current heavy metals such as mercury ion, lead ions and arsenic ions as well as operation, complex data processing analysis, and difficult on-site detection analysis. The apparatus is a minisize darkroom arranged below the intelligent equipment, a glass fiber paper-based chip is fixed at bottom in the minimized darkroom, reaction zones and non-reaction zones are arranged on the glass fiber paper-based chip at intervals, an optical hardware apparatus is arranged at the top of the glass fiber paper-based chip, and a photo-taking program and a heavy metal ion concentration value calculating program are arranged on the intelligent equipment. The apparatus and the method can simultaneously detect Pb<2+>, Hg<2+>, and As<3+>, cost is low, a process is simple, and is benefit for on-site detection and analysis of heavy metal concentration in the polluted water body, detection is convenient, fast and accurate, and the apparatus and the method are benefit for experiment detection examination and convenient for real-time detection of pollution condition in the water body in life.