Abstract: According to Euler buckling model, the end restraint coefficient μ was characterized to analysis the interfacial interaction of Z-pin in sandwich structures.And it is inversely proportional to the integration degree with factsheets and instability of Z-pin during compressive process.On this basis, compression tests of K/X-cor structures with different Z-pin configurations were performed, and the influence of Z-pin diameters and bending lengths on compression property were studied.With the use of microscopic observation and "mixture law", the enhance efficiency of Z-pin diameters on K-cor and X-cor structures were compared.With the consideration of mass loss, the influence of bending length on strength and stiffness ratio were analyzed.And the semi-analytical formulas for optimal bending length was given.The results reveal that large diameter pin in K-cor structure has better reinforcement efficiency and causes less structural damage compared with X-cor structure.With the increase of bending length, the strength and stiffness ratio increase first and then decrease.There exists the optimum bending length value on different circumstances.