The invention discloses a flexible wearable paper-based strain sensor and a preparation method thereof. The flexible wearable paper-based strain sensor comprises an insulated layer, a conductive layer, a guide wire fixing unit and guide wires, wherein the insulated layer is arranged at the bottom end; the conductive layer is arranged on the upper surface of the insulated layer; one guide wire is connected to each of two ends of the conductive layer; the guide wires are connected with a measuring instrument; the insulated layer is paper base with insulating characteristic. The flexible wearable paper-based strain sensor has the benefits that of being simple to prepare, low in cost, good in product performance, simple and convenient to operate, low-carbon and environment-friendly, simple in structure, high in strain detecting speed, can be worn on finger joints, wrist junctions, knee joints of a human body, can be fixed to objects of furniture, books, building structures and the like for strain detection, and has a wide application prospect in the fields of kinesiology, structure safety monitoring, and the like.