Based on the direct shear test method and utilizing 3D printing technology, experimental research is conducted on the strength characteristics of cohesive soil with different JRC contact surfaces. The contact surface with a certain roughness exhibits its characteristics only under lower normal stress. As the normal stress increases, the shear surface becomes an internal shear band within the soil, and the shear characteristics of the contact surface closely resemble those of soil. Therefore, different levels of normal stress significantly affect the characteristics of the soil-rock contact surface. When JRC < 7.3, under low normal stress, a smaller JRC leads to lower peak shear stress at the contact surface. However, under high normal stress, the peak shear stress at contact surfaces with different JRC values tends to be closer together. The interface friction angle slightly increases as JRC decreases, while cohesion decreases with a decrease in JRC. A relationship between interface cohesion (C), friction angle (φ), and interface roughness (JRC) is proposed.