The invention discloses a probe mechanism of an oil and gas pipeline crack detector. The probe mechanism of the oil and gas pipeline crack detector comprises a signal excitating and acquiring mechanism, wherein a spring connecting rod supporting mechanism and a spring slide block supporting mechanism are connected at the front end and the back end of the signal excitating and acquiring mechanism through universal rotating mechanisms respectively; the spring connecting rod supporting mechanism and the spring slide block supporting mechanism are fixedly arranged on a framework of the crack detector; the signal excitating and acquiring mechanism comprises a long arm-shaped connecting base body; transversely arranged supporting wheels are pivoted on the upper parts of the front end and the back end of the connecting base body; an iron core is arranged on the connecting base body; a probe shell assembly is arranged above the iron core and on the middle part of the connecting base body; the front part and the back part of the probe shell assembly are pivoted on the iron core through a front probe arm and a back probe arm respectively; an exciting circuit assembly fixed on the iron core is arranged below the probe shell assembly; magnets are arranged between the probe shell assembly and the front and back supporting wheels respectively; and steel brushes are arranged above the magnets. The probe mechanism of the oil and gas pipeline crack detector is always tightly adhered to the inner wall of a pipeline while passing through a welding seam of the pipeline, so that the detection precision and the sensitivity of the detector can be improved.