A hydrogen gas sensor utilizing electrically isolated tunneling magnetoresistive sensing elements is provided. The hydrogen gas sensor comprises: a substrate in an X-Y plane, tunneling magnetoresistive sensors located on the substrate, and a hydrogen sensing layer located on the tunnel magnetoresistive sensors. The hydrogen sensing layer and the tunneling magnetoresistive sensor are electrically isolated from each other. The hydrogen sensing layer includes a multi-layer thin film structure formed from palladium layers and ferromagnetic layers, wherein the palladium layers are used for absorbing hydrogen in the air that causes a change in the orientation angle of a magnetic anisotropy field in each of the ferromagnetic layers in the X-Z plane into an X-axis direction. The tunnel magnetoresistive sensors are used for detecting a magnetic field signal of the hydrogen sensing layer, wherein the magnetic signal determines the hydrogen gas concentration. This hydrogen gas sensor ensures measurement safety.