Abstract: The anchorage body diameter is the key factor of the pullout resistance and the reliability of jet grouting anchor. Based on the physical process of jet grouting breaking soil, a convenient calculation method for anchorage body diameter for application is proposed. For the support of 32 m deep-foundation pit in Sanmen Nuclear Power Station, in situ tests are designed to validate the proposed method by comparing 3 excavated anchors of the 12 test anchors. The effect of jet parameters on the anchorage body diameter is also analyzed. The results reveal that under the influences of incomplete breadage and large particle sedimentation of soil, the calculated diameters are smaller than the test data, and the difference between them is larger when the jet pressure is lower and the drilling speed is faster. The jet grouting anchor with flake burrs in surface is approximate to ellipse in shape because of the spiral motion and vibration of the drill pipe. The higher the jet pressure, the faster the drilling speed, leading to more irregular shape. Under the same condition, reaming quality is better by increasing the nozzle diameter and using two times of reaming. In order to improve the reaming efficiency and to avoid the appearance of discontinuous jet profile, the drilling speed should be designed in a suitable range.