Earthen materials have been used as economic building materials since ancient times and continue to be used today, particularly in our modern society that pursues sustainability. As a form of agricultural waste, straw stalks are reused in civil engineering to avoid being burnt, which not only saves costs but also avoids environmental impacts. In the following paper, we present an experimental study on the mechanical properties of rammed red clay reinforced by straw fibers. Straw stalks were cut into different lengths and mixed evenly with red clay in different proportions before being compacted. The compressive strength, flexural strength, and shear strength of the stabilized rammed straw were analyzed. The results show that straw stalks, as a single reinforcing material, can significantly improve the mechanical properties of rammed red clay. Straw stalks had varying effects on improving the mechanical indexes of rammed red clay. When the length of the straw stalks was 15 mm and the straw stalk content was 0 Sust.3%, the straw stalks had the best effect on improving the mechanical properties of rammed red clay.