A monolithic three-axis linear magnetic sensor, the sensor comprising: a substrate in an XY plane, the substrate having an X-axis sensor, a Y-axis sensor and a Z-axis sensor integrated thereon, each of which comprises one or more identical magnetoresistive sensing elements that are electrically interconnected, for detecting components of a magnetic field in an X-axis direction, a Y-axis direction and a Z-axis direction, respectively; the X-axis sensor comprising a referenced bridge and at least two X ferromagnetic flux guides, a reference arm and a sensing arm of the referenced bridge being arranged alternately and each comprising the one or more identical magnetoresistive sensing elements (12, 11) that are electrically interconnected; the magnetoresistive sensing elements on the reference arm being placed above or beneath the X ferromagnetic flux guides, and being arranged along length directions of the X ferromagnetic flux guides to form reference element series; the magnetoresistive sensing elements on the sensing arm being placed at gaps between adjacent X ferromagnetic flux guides, and being arranged along the length directions of the X ferromagnetic flux guides to form sensing element series; the Y-axis sensor comprising a push-pull bridge, a push arm and a pull arm of the push-pull bridge each being correspondingly provided thereon with at least two Y ferromagnetic flux guides (23, 24), the push arm and the pull arm being arranged alternately and each comprising one or more identical magnetoresistive sensing elements (13, 14) that are electrically interconnected, and the magnetoresistive sensing elements being placed at gaps between adjacent respective Y ferromagnetic flux guides; the Z-axis sensor comprising a push-pull bridge and at least one Z ferromagnetic flux guide, a push arm and a pull arm of the push-pull bridge being arranged alternately and each comprising the one or more identical magnetoresistive sensing elements (15, 16) that are electrically interconnected; the magnetoresistive sensing elements on the push arm and the pull arm being placed at respective sides of the bottom or the top of the at least one Z ferromagnetic flux guide, and being arranged along the length direction of the Z ferromagnetic flux guide; magnetization directions of pinned layers of all the magnetoresistive sensing elements in the X-axis sensor, the Y-axis sensor and the Z-axis sensor being all the same, and when there is no ferromagnetic flux guide, sensing directions of all the magnetoresistive sensing elements being the X-axis direction; wherein the X axis, the Y axis and the Z axis arc pairwise orthogonal to each other; and wherein the ferromagnetic flux guides are each a rectangular strip of a soft ferromagnetic alloy. a substrate in an XY plane, the substrate having an X-axis sensor, a Y-axis sensor and a Z-axis sensor integrated thereon, each of which comprises one or more identical magnetoresistive sensing elements that are electrically interconnected, for detecting components of a magnetic field in an X-axis direction, a Y-axis direction and a Z-axis direction, respectively; the X-axis sensor comprising a referenced bridge and at least two X ferromagnetic flux guides, a reference arm and a sensing arm of the referenced bridge being arranged alternately and each comprising the one or more identical magnetoresistive sensing elements (12, 11) that are electrically interconnected; the magnetoresistive sensing elements on the reference arm being placed above or beneath the X ferromagnetic flux guides, and being arranged along length directions of the X ferromagnetic flux guides to form reference element series; the magnetoresistive sensing elements on the sensing arm being placed at gaps between adjacent X ferromagnetic flux guides, and being arranged along the length directions of the X ferromagnetic flux guides to form sensing element series; the Y-axis sensor comprising a push-pull bridge, a push arm and a pull arm of the push-pull bridge each being correspondingly provided thereon with at least two Y ferromagnetic flux guides (23, 24), the push arm and the pull arm being arranged alternately and each comprising one or more identical magnetoresistive sensing elements (13, 14) that are electrically interconnected, and the magnetoresistive sensing elements being placed at gaps between adjacent respective Y ferromagnetic flux guides; the Z-axis sensor comprising a push-pull bridge and at least one Z ferromagnetic flux guide, a push arm and a pull arm of the push-pull bridge being arranged alternately and each comprising the one or more identical magnetoresistive sensing elements (15, 16) that are electrically interconnected; the magnetoresistive sensing elements on the push arm and the pull arm being placed at respective sides of the bottom or the top of the at least one Z ferromagnetic flux guide, and being arranged along the length direction of the Z ferromagnetic flux guide; magnetization directions of pinned layers of all the magnetoresistive sensing elements in the X-axis sensor, the Y-axis sensor and the Z-axis sensor being all the same, and when there is no ferromagnetic flux guide, sensing directions of all the magnetoresistive sensing elements being the X-axis direction; wherein the X axis, the Y axis and the Z axis arc pairwise orthogonal to each other; and wherein the ferromagnetic flux guides are each a rectangular strip of a soft ferromagnetic alloy.