Taking the NY-300/40 compression strain clamp as an example, the three-dimensional finite element model of the strain clamp-conductor system is established using LS-DYNA software. The tensile behavior of the strain clamp with standard clamping length (110mm) is simulated and compared with the experimental results. On this basis, the tension capacities and failure modes of the strain clamp under different clamping lengths between the steel anchor and the steel core are also analyzed. The results show that the grip strength of the strain clamp mainly comes from the compression between steel anchor and steel core. Under the condition of standard clamping length, the tension bearing capacity of the strain clamp can meet the design requirements, and because the clamping length is enough, the failure mode of tension clamp is the breakage of the aluminum strands rather than the steel core pulled out. When the clamping length between the steel anchor and steel core is insufficient, the grip strength of the strain clamp decreases gradually with the reduction of the clamping length. Although the absolute value of the grip strength decreases slightly, the failure mode of the tension clamp gradually changes from the mode of the aluminum strands breaking to the mode of the steel core being pulled off from the steel anchor. As far as the strain clamp concerned in this paper, the corresponding clamping length between the steel core and the steel anchor is between 50 mm and 60 mm, when the failure mode shifts from one to another.