To address the safety problems caused by clips being squeezed by jacks and wire slipping in the tensioning process of flat anchorages, we designed a limit plate to be used with a flat anchorage, and we studied the mechanical properties of the anchorage system after adding the limit plate through numerical simulation. Lastly, the limit plate was created and applied in a practical engineering scenario to test its safety performance. The results showed that the newly designed limit plate changed the butt position of the jack during tension, increased the hole distance, and hid the clips in the hole position of the limit plate, thus mitigating the safety hazard caused by the narrow surface tension construction in practice. The limit plate alleviated the stress concentration on the anchorage, and the extreme stress value decreased by 10–13%. Adverse effects, such as stress concentration caused by tension, were transferred to the replaceable limit plate, thus improving the reliability of the flat anchorage. The symmetrical tensioning scheme represented by sequential tensioning of holes 1, 4, 2, 5, and 3 is recommended, which produced the lowest extreme stress value of 685.55 kPa, which is 22.42 kPa lower than the maximum value of various other schemes.