The embodiment of the invention discloses an optical fiber isolator and an optical fiber laser, and relates to the technical field of lasers. The optical fiber isolator comprises one or more light beam isolation structures, a coupling collimator, a transmitting energy fiber and an output collimator, wherein the transmitting energy fiber is connected with the coupling collimator and the output collimator; the light beam isolation structures comprise diaphragms, first beam splitters, magnetic optically-active crystals, magnets, half wave plates, fixing devices and second beam splitters, wherein the centers of light through holes of the diaphragms and the first beam splitters, the magnetic optically-active crystals, the half wave plates and center shafts of the second beam splitters are located in the same straight line; the optical-axis direction of the first beam splitters is mutually perpendicular to the optical-axis direction of the second beam splitters; the magnetic optically-active crystals are located in magnetic field areas of the magnets; the fixing devices drive the half wave plates to rotate to adjust the optical rotation angles of the half wave plates. The optical fiber isolator is simple in isolation degree structure and convenient to use.