Abstract ： Research purposes ： Horizontal limit bearing capacity under current design of gravity anchorage based on friction design condition is often conservatively estimated. The estimated value without consideration of synergy and joint bearing mechanism of gravity anchorage and base is greatly deviated from practical one. Using friction test of rock base in adit，monitoring section of deep displacement under base bottom and numerical simulation experiment，the synergy and joint bearing mechanism of gravity anchorage and base is discussed in the paper. Research conclusions ：( 1) Fail mode presented by limit test proves that gravity anchorage is not friction bearing，but anchorage and base joint bearing. (2) The limit bearing capacity of anchorage ； rock base can be divided into two stages and contains three effects，first being friction efect supported by friction limit bearing capacity of anchorage base bottom，second is clamping effect presented by clamping rock mass shearing limit capacity，third is buried depth effect enhanced the former two limit bearing parts by refilling soil weight on base and structure. ( 3 ) The estimation formula for horizontal limit bearing capacity of gravity anchorage witli above three effects considered is built, which is checked by project case, limit result of formula being 9. 6 P is close to that of numerical test being 8. 0P, these prove precision of tlie formula and conform to practical fail mode. (4) The achievement above can be used in design and monitoring fields of new type gravity anchorage.