The invention discloses a method for detecting the electrode plate joint shedding phenomenon of an electrothermal concrete pavement. The method comprises the steps of S1, measuring the current strength Ii of each power supply branch of the electrothermal concrete pavement, and judging whether each power supply branch is a suspected faulty line or not, wherein i is larger than or equal to 1; S2, powering on each suspected faulty line, and measuring the strengths of magnetic fields at each measuring point of a live line and each measuring point of a null line; S3, through the formula (img file = 'DDA 0001226839360000011. TIF 'wi = '177 'he = '118 '/), calculating the ratio of magnetic field strengths at each measuring point measuring point of the live line and each measuring point of the null line, wherein Ri represents the ratio of magnetic field strengths at the i measuring point, mli and mni respectively represent the magnetic field strengths at the i measuring points of the live line and the null line; S4, calculating the change rate of the magnetic field strength according to each magnetic field strength, and determining the shedding position of an electrode plate joint according to the change rate of the magnetic field strength. Based on the method provided in the invention, the specific shedding position of the electrode plate joint can be rapidly and accurately determined. Therefore, the lossless diagnosis for the electrode plate joint shedding phenomenon of the electrothermal concrete pavement can be realized.