Abstract: A method for forming a magnetic sensor includes: forming a hard mask film on a tantalum nitride film; forming a patterned photoresist layer on the hard mask film; implementing an isotropic dry etching process to the hard mask film by taking the photoresist layer as a mask, so as to form a hard mask layer; and implementing an etching process to the tantalum nitride film and the magnetic film by taking the hard mask layer as a mask, so as to form a tantalum nitride layer and a magnetic resistive layer. As an isotropic dry etching process is implemented to the hard mask film, the hard mask film located which is above the other sidewalls and is not used for forming the magnetic sensor can be effectively removed. In addition, shadow effect will not take place, thus dimension of the magnetic sensor formed is able to be easily controlled.