The invention discloses a flexible monitoring device and method of landslip. The device comprises an upper cavity and a lower cavity, wherein the upper cavity and the lower cavity are limited in a sleeve and communicate with each other, an anchor cable is arranged in the lower cavity, a lower end of the anchor cable extends out of the lower cavity, the anchor cable does downward and unidirectionalmovement in the sleeve during usage, an anchoring end is arranged at a bottom end of the anchor cable, the anchor cable penetrates through a sliding body and is fixedly arranged on a sliding bed by the anchoring end, a sliding head is connected with a top end of the anchor cable, the sliding head is arranged in the upper cavity in an initial state, the sliding head can do downward and unidirectional movement, a rubber pipe sleeves an outer side of the sleeve and penetrates through the sliding body, particles are filled between the rubber pipe and the sleeve, the sleeve cover is fastened on the sleeve and covers the upper cavity, and a sound emission sensor is arranged on an upper surface of the sleeve cover. Therefore, the improved flexible monitoring device of the landslip is provided, the device is difficult to damage by deformation of the landslip during the monitoring process of the landslip, the lifetime of the device is prolonged, and the device is more suitable for monitoring the landslip.