An optical concentration testing device comprising an optical concentration sensor protective casing, wherein, said optical concentration sensor protective casing comprises an outer cover, and a bubble isolation shield embedded on an inner side of the outer cover; the outer cover is provided with a convection hole; and the bubble isolation shield is provided with a liquid intake hole; said optical concentration sensor protective casing further comprises a middle fixing frame and an air hole baffle plate, wherein the outer cover is provided with a first exhaust hole, the air hole baffle plate covers the first exhaust hole, and an interstice exists between the air hole baffle plate and the first exhaust hole, wherein the bubble isolation shield is provided with a second exhaust hole, the first exhaust hole and the second exhaust hole intercommunicate, wherein the outer cover and the bubble isolation shield are mounted at one end of the middle fixing frame, the bubble isolation shield and an inner space of the middle fixing frame form a testing section for a solution to be tested, said optical concentration testing device further comprises a sensor body configured to test the concentration of the solution and mounted in the interior of the optical concentration sensor protective casing, and characterized in that, the sensor body is provided with a testing gap opening in a horizontal direction and disposed on a horizontal side wall of the sensor body, the sensor body is mounted within the middle fixing frame, and the testing gap has slanted side walls, so that if bubbles in the solution to be tested are not eliminated and enter into the testing section, the remaining bubbles in the testing section will float up along the slanted side walls of the testing gap and be discharged from the second exhaust hole. said optical concentration sensor protective casing comprises an outer cover, and a bubble isolation shield embedded on an inner side of the outer cover; the outer cover is provided with a convection hole; and the bubble isolation shield is provided with a liquid intake hole; said optical concentration sensor protective casing further comprises a middle fixing frame and an air hole baffle plate, wherein the outer cover is provided with a first exhaust hole, the air hole baffle plate covers the first exhaust hole, and an interstice exists between the air hole baffle plate and the first exhaust hole, wherein the bubble isolation shield is provided with a second exhaust hole, the first exhaust hole and the second exhaust hole intercommunicate, wherein the outer cover and the bubble isolation shield are mounted at one end of the middle fixing frame, the bubble isolation shield and an inner space of the middle fixing frame form a testing section for a solution to be tested, said optical concentration testing device further comprises a sensor body configured to test the concentration of the solution and mounted in the interior of the optical concentration sensor protective casing, and characterized in that, the sensor body is provided with a testing gap opening in a horizontal direction and disposed on a horizontal side wall of the sensor body, the sensor body is mounted within the middle fixing frame, and the testing gap has slanted side walls, so that if bubbles in the solution to be tested are not eliminated and enter into the testing section, the remaining bubbles in the testing section will float up along the slanted side walls of the testing gap and be discharged from the second exhaust hole.