Transparent soft rock exhibits significant application value in geotechnical engineering model tests, yet systematic studies on the factors and mechanisms influencing its shear strength remain limited. In this study,fused quartz sand, nano-scale hydrophobic silica powder, No. 15 white oil, and n-dodecane were selected as primary transparent cementing materials to investigate the effects of silica powder content, quartz sand particle size, and sample dry density on the shear strength of transparent soft rock. Theoretical values of cohesion and internal friction angle for the Chongqing Jigongzui Tunnel model test were determined using dimensional analysis. Orthogonal experiments were conducted to optimize the material ratio and further analyze these influencing factors.Results demonstrate that, Increased silica powder content leads to an approximately linear enhancement in cohesion, while the internal friction angle remains nearly unaffected.Higher proportions of fine particles result in an initial decrease followed by an increase in internal friction angle, with negligible impact on cohesion.Elevated dry density induces a rapid-to-gradual ascending trend in cohesion, while the internal friction angle exhibits initial stability followed by a progressive increase.The optimized ratio (4% silica powder, particle size group D with 75% 0.5-1 mm particles, and dry density of 1.35 g/cm3) shows high compatibility with the surrounding rock parameters of the Chongqing Jigongzui Tunnel. This research provides theoretical and technical foundations for applying transparent soft rock in geotechnical model testing..