The invention discloses an optical fiber sensor capable of measuring stress direction. The optical fiber sensor comprises a laser, a first polarization controller, a sensing fiber, a second polarization controller, a polarization analyzer and a computer Matlab algorithm, which are connected in sequence. When the sensing fiber is subjected to an external stress, the polarization analyzer records information of rotation of a polarization state around a principal axis of the external stress on a Poincare sphere; and the Matlab algorithm calculates an actual direction angle of the external stress based on linear relation between a direction angle of the external stress principal axis with respect to a reference external stress principal axis and the actual direction angle of the external stress.