The invention relates to a resistivity-based coal seam hydraulic fracture blind area detection method which is suitable for detecting the location and range of a coal seam hydraulic fracture blind area, belonging to a coal rock geophysical detection method. A coal body has resistivity, the resistivity of the coal body is reduced after hydraulic fracture, but the coal body resistivity in a fracture blind area is not changed significantly, according to the principle, through using an electrical prospecting apparatus to measure the resistivity of the coal body and comparing coal body resistivity before and after fracture, the existence of the blinding area and the specific position and range size of the blind area can be rapidly determined, and the method has the advantages of low detection cost, short time, high efficiency, and high convenience.