This study investigates the asymmetrical arching phenomenon in inclined granular deposits by performing the DEM simulations of trapdoor tests. The results indicate that the weakest arching effect occurs at deposit inclination angles of 30° ∼ 45°, evidenced by the highest arching ratio on the trapdoor, largest deposit settlement, and lowest fabric anisotropy intensity. The asymmetrical arching effect is manifested by lower arching ratios, greater deposit settlements and larger fabric anisotropy magnitudes on the left part beside the trapdoor compared to the right part. The arching asymmetry depends on the angle Ψ formed between the potential failure plane's orientation and the deposit inclination direction, and this angle (Ψ_L) for region L is on average lower than that (Ψ_R) for region R. A larger Ψ_R leads to a more notable inter-particle locking effect and a higher resistance to deformation for region R, which further causes larger arching ratios and less remarkable deposit settlements. Moreover, the arching asymmetry degree is positively correlated with the discrepancy between Ψ_L and Ψ_R. The disparity of mechanical responses between regions L and R aggravates with increasing Ψ_R – Ψ_L, and the strongest asymmetrical arching effect occurs around θ = 30°, where Ψ_R – Ψ_L takes the maximum value.