The invention discloses a string-type strain gauge used for concrete spraying, and belongs to the technical field of tunnel construction. The strain gauge solves the problem that existing devices cannot realize position adjustment, and then cause the devices to be unable to realize self-protection. Technical features of the strain gauge are that the strain gauge includes a protection shell body and an upper cover plate, two sides of the protection shell body are both provided with vertical through grooves, the upper cover plate is disposed above the protection shell body, the top of the protection shell body is provided with slots, lower ends of the upper cover plate are connected with the slots through buckles, two strain gauge installation boxes are symmetrically disposed inside the protection shell body, strain gauge components are disposed in the strain gauge installation boxes, and a protection mechanism used for protecting the strain gauge installation boxes is disposed at an intermediate position inside the protection shell body. According to the embodiment of the invention, a position adjustment component and driving components are disposed, positions of the strain gauge installation boxes can be flexibly adjusted, normal working of the strain gauge components is guaranteed, and interference caused by an external environment to the strain gauge components is avoided atthe same time.