The invention discloses a dual-oil-path mechanical control variable damping passive oil pressure shock absorber for a railway vehicle, and belongs to the field of oil pressure shock absorbers. The shock absorber comprises an oil cylinder assembly, a piston assembly and a damping characteristic conversion valve assembly. The oil cylinder assembly comprises a work cylinder and an oil storage cylinder, the piston assembly comprises a piston with two ends being free of communicating with an oil path, the piston is arranged in the work cylinder in a sliding manner, and the work cylinder is dividedinto a stretching oil cavity and a compressing oil cavity, the damping characteristic conversion valve assembly comprises at least two stretching oil path adjusting valves arranged in parallel and atleast two compression oil path adjusting valves arranged in parallel, liquid inlet ends of the stretching oil path adjusting valves and the compression oil path adjusting valves communicate with a stretching oil cavity and a compressing oil cavity correspondingly, and the liquid outlet ends of the stretching oil path adjusting valves and the compression oil path adjusting valves communicate to theoil storage cylinder through different oil paths. According to the shock absorber, according to different application speeds or different running conditions of the vehicle, mechanical switches are adopted for converting different damping characteristics, and damping coefficients before and after loading of the shock absorber can be converted.