Abstract: The three-spring probe mechanism is not applicable for small-diameter detectors. In this regard, the probe mechanism of the detector was improved. First, the supporting-spring sliding connection was used between probe shell and supporting springs, instead of the screw fixed connection. Second, auxiliary spring of the three-spring probe mechanism was removed, so that there are no collisions between the auxiliary spring and other connected mechanisms like screws and rivets on the probe arms after probe arms and springs were cut short. Third, rigid probe arms were replaced by spring arms, so as to balance the spring support force after the removal of the auxiliary spring. Fourth, an elastic cushion was used between probe shells and spring arms, so that the rear of the probe shell was kept upwarped from falling down. Based on mechanical performance tests and pull tests, the improved probe mechanism is characterized by stability, wear resistance and anti-tremor capacity, with the ultimate compression size of 30 mm. It is very applicable to small-diameter detectors or the equipments with limited radial space. When the springs and the probe arms are extended in size, this probe mechanism can also be applied to large-diameter detectors and has wide application range.