Abstract: In the existing specifications and codes, the factor of safety of anchor against pull-out is generally defined by considering tensile strength of steel bar/strand, bond strength of grout and the steel bar/strand, and bond strength of grout and surrounding rock/soil. It results in three different types of factors of safety, which are being applied in practice. The current China ' s specifications and codes suggest the same allowable value for the above three different types of factors of safety. Actually, there is quite difference among them due to different pull-out failure mechanisms of tendon. In view of this limitation, the difference among them is studied and discussed under the same reliability (or failure probability) by using the reliability analysis, and the criteria for determining the factor of safety of anchor against pull-out are proposed.