Abstract: In order to solve the problem of how to temporarily carry heavy vehicle whose load magnitude is far more than that of its design load,for long-span masonry arch bridge,a balance-loading method,by which heavy cargoes can be bore not by structural retrofitting but dynamically moving supplement vehicle,was presented in this paper.Firstly,the relation between ultimate bearing capacity of masonry arch and deviation of thrust line from neutral axis of its section was analyzed.It was concluded that if loads were properly distributed,the arch structure could afford to bear far more heavy loads.Secondly,based on detailed analysis of calculation method of ultimate bearing capacity for masonry elements eccentrically loaded,the eccentricity of resultant forces on section was chosen as a critical parameter to qualitatively determine if the section had sufficient capacity without detailed calculation.With the eccentricity,the method of temporarily carrying heavy vehicle without structural strengthening was proposed,and the corresponding procedure and key technical measures were also discussed.Finally,for a concrete arch bridge with box section and span length of 130 m a detailed plan of carrying a vehicle of total 400 tons weight was presented.Both theoretical study and practice show that the proposed method is feasible.