Abstract: The reliability analysis of a single pile is the basis of reliability analysis of pile groups. However, the ultimate bearing capacity of the pile and the reliability index obtained using different failure criteria may not be the same due to the differences in failure criteria used in different countries. Therefore, the reliability of pile groups is various according to different failure criteria. The different failure criteria from various countries are examined, and a bias factor defined with respect to s-lgt criterion usually used in China is introduced. Meanwhile, the calculation method of reliability of pile groups considering different criteria is presented using the bias factors and pile group effect, which provides a theoretical basis to calibrate the reliability levels of pile foundation associated with various failure criteria. The results from case studies indicate that considerable reliability index of pile groups can be obtained according to different failure criteria, but the safety of pile group foundation is not variable. Therefore, before judging the safety of pile group foundation, the failure criterion should be chosen, and it can cause relatively significant loss to the project if the calculated reliability index is only used to evaluate the safety of foundation. In addition, the pile group effect, system effect, soil type and cap type have significant influences on the reliability of pile group foundation. Therefore, their contribution to the reliability should be considered in the reliability analysis of pile group foundation.