The invention discloses a device and a method for testing water absorbing property of silicon rubber material under stress conditions, and relates to the technical field of power grids, which are applied to study the influence of mechanical strain on water absorbing property and moisture absorbing property of silicon rubber. The device for testing the water absorbing property of the silicon rubber material under the stress conditions comprises a base, wherein two vertical plates are fixedly arranged on the base at interval; a to-be-tested sample which is made of the silicon rubber material is arranged between the two vertical plates; the vertical plates are connected with the to-be-tested sample through connecting structures; the to-be-tested sample can be tensioned or compressed by operating the connecting structures; when the to-be-tested sample is tensioned or compressed to the preset length, the connecting structures are fixedly connected with the corresponding positions of the vertical plates through positioning structures. The device is used for testing the water absorbing property of the material.