The invention discloses a high-sensitivity all-optical cesium atom magnetometer and belongs to an atom magnetometer. The magnetometer is provided with a magnetic shielding tube, a Cs atom gas chamber is placed in the magnetic shielding tube, a three-axis Helmholtz coil is placed around the Cs atom air chamber, and a pump light opening, a detection light opening and am emergent light opening are respectively formed in the magnetic shielding tube. The Cs atom gas chamber is cuboid, four surfaces, used for passing through deflection light to form reflection, excepting incident light and emergent light local parts of the detection light, the Cs atom air chamber are plated with polarization-maintaining films, and the other two surfaces used for passing through pump light are not plated with films. The detection light emitted by a detection light laser enters the Cs atom gas chamber through a polarizing film and a small aperture diaphragm and is emergent after reflected on all the surfaces of the gas chamber repeatedly, the polarization plane of the emergent light rotates by a one-degree angle, one drip of Cs, 100Torr of He gas and 20Torr of N2 gas are put into the Cs atom gas chamber, and the Cs atom gas chamber works at normal temperature. The high-sensitivity all-optical cesium atom magnetometer has the advantages of being simple in structure and still capable of keeping high sensitivity without being heated.