The invention discloses a 2*2 long period fiber Bragg grating coupler which comprises a force applying device, and two pieces of closely contacted and parallel arranged bare optical fibers without protective layers, namely, transmission fiber and coupling fiber. The force applying device periodically applies radial pressure with period Lambada being hundred-micron magnitude on the axial propagation of the optical fibers, thus gratings with equivalent spatial variation are written on the axial propagation of the bare optical fibers. When spatial period of fiber Bragg grating causes fiber core fundamental modes and higher order cladding modes to satisfy the phase position matching condition, the fiber core fundamental modes and the cladding modes of the transmission fiber and the coupling fiber perform intercoupling; besides, cladding modes of the transmission fiber and the coupling fiber perform intercoupling under action of evanescent field. Based on the couplings, periodical radial pressure plays the role of a coupler on the two pieces of bare optical fibers. As the long period fiber Bragg grating is only generated by external force, the long period fiber Bragg grating coupler is a wavelength choice direction coupler easy to write and erase, and can be applied to optical communication network as a flexible add/drop multiplexer and the like.