The interlock of a roll formed U-section sheet steel piling under loading was analyzed by means of numerical simulation,and meanwhile the tensile failure experiment was conducted.The results indicated that under the same load,the interlock corners of roll formed steel piling are not only the regions with the lowest safety factor,but also the regions with the highest stress;there are two slippages in the tensile instability process of interlock.Each slippage can be regarded as a failure,and different types of failure mode should be used to evaluate the performance of steel pilings according to different applications.Due to the work hardening effect during the roll forming process,the hardness of the interlock material increases by 16%compared with that of the original sheet steel.It was also found that the instability strength obtained in tensile failure test is only 15.6%of the tensile strength of the original sheet steel. The interlock of a roll formed U-section sheet steel piling under loading was analyzed by means of numerical simulation, and meanwhile the tensile failure experiment was conducted.The results indicates that under the same load, the interlock corners of roll formed steel piling are not only the regions with the lowest safety factor, but also the regions with the highest stress; there are two slippages in the tensile instability process of interlock. Each slippage can be considered as a failure, and different types of failure mode should be used to evaluate the performance of steel pilings according to different applications. Due to the work hardening effect during the roll forming process, the hardness of the interlocking material increases by 16% compared with that of the original sheet steel. in tensile failure test is only 15.6% of the tensile strength of the original sheet steel.