A method of detecting a target molecule concentration comprises the following steps: (1) coupling a first molecular probe to a surface of a magnetic bead to form a magnetic bead probe, and coupling second molecular probes to surfaces of target particles to form target probes; (2) mixing the magnetic bead probe with a target molecule solution so as to capture a target particles at a surface of the magnetic bead probe; (3) adding the target probes, combining the target molecule with the second molecular probes, and forming a magnetic bead probe-target molecule-target probe composite; (4) removing an unreacted target probe; (5) adding an eluent, dissociating a structure of the magnetic bead probe-target molecule-target probe composite into the magnetic bead probe, target molecule, and target probe; (6) extracting a solution obtained from Step (5) to prepare a specimen on a microscope slide, counting and calculating, using a microscope, a total number of target probes, and calculating a target molecule concentration accordingly. The detection method provides increased reliability and sensibility.