Soil internal forces (SIFs), including electrostatic, hydration, and Van der Waals forces, are deemed as the important forces to induce aggregate breakdown and then splash erosion. Exploring the mechanisms underlying splash erosion is crucial for effective soil erosion prevention. However, it is still unclear how the combined effects of soil internal and external (raindrop impact) forces influence splash erosion. In this study, to explore the detachment and displacement characteristics of aggregate fragments under the combined effects of soil internal and external forces, Loessal soil and Lou soil were collected from the Loess Plateau for indoor simulated rainfall experiments. Electrolyte solutions with different concentrations (from 10(-5) to 1 mol L-1) were selected as simulated rainfall raindrops to quantitatively regulate SIFs, and two rainfall heights (1.2 and 1.5 m) were set to regulate raindrop impact force. Our results demonstrated that an electrolyte concentration of 10(-2) mol L-1 represented a critical point affecting the net pressure of SIFs, which increased rapidly as electrolyte concentration decreased from 1 to 10(-2) mol L-1, accompanied by a corresponding increase in splash erosion mass. The relationship between net pressure and splash erosion mass (SEM) was well-described by exponential functions (R-2 > 0.92). The SEM increased with rainfall kinetic energy (controlled by rainfall height), particularly within a splash distance of 0-10 cm. Specifically, the average increases in SEM for Loessal soil and Lou soil were 0.10 g and 0.32 g, respectively. The <0.053 mm fragments constituted the majority of ejected soil material (over 60%), and their proportion exhibited a decreasing trend as rainfall kinetic energy increased. Overall, the combined effects of soil internal and external forces control the detachment and displacement of aggregate fragments during rainfall. This study provides new insights into splash erosion mechanism, thereby potentially reducing splash erosion through conjointly regulating-controlling soil internal and external forces.