The invention relates to a probe spring of a pipeline corrosion detector which detects the metal loss degree of a steel pipeline on line and relates to the technical fields of measuring magnetic variables, measuring the linear sizes of thickness and pipeline systems. The invention is characterized in that the probe spring is an elastic ring made by polyurethane. The probe spring is an elastic ring approximating to a triangle or a trapezium made by the polyurethane; a front bevel edge on the advancing direction of the detector is thinner than a back bevel edge; the middle upper part of the back bevel edge bends a little to the front; besides, the upper end and the lower side of the back level edge are provided with fixing holes. As the flexible elasticity, the elastic ring is applied on the probe spring of the pipeline corrosion detector to lead the detector to be stable when passing through a weld bead and lead the probe not to be impacted, thus prolonging the service life of the probe; besides, the elastic ring is hard to be damaged, has long service life, is easily processed and is an ideal probe spring.