The invention relates to a slope seabed pipeline in-place stability mechanical loading analog device and a method thereof. The device is characterized by comprising a transparent soil groove which is internally provided with a soil body with an inclined upper surface; the upper surface of the soil body is laid with a model pipeline; the model pipeline is provided with a mechanical loading device used for applying tensile force; and the mechanical loading device is provided with a tensile force sensor, a vertical laser displacement sensor and a parallel laser displacement sensor. The device isingenious in structure and design, and the method is convenient for operation and easy to implement, so that the invention can be widely applied to analogue measuring process of slope seabed pipelinein-place stability.