The invention provides an all-fiber current sensor for internal measurement of high voltage equipment. The current sensor comprises a sensing unit and fibers; the sensing unit is arranged in the high voltage equipment, and used to collect branch current signals in the high voltage equipment; the fibers include first and second high-voltage segment fibers, and are used to transmit the branch current signals in the high voltage equipment; the first high-voltage segment fiber is connected with the sensing unit and arranged in the high voltage equipment, and a helix tube is arranged outside the first high-voltage segment fiber; and the second high-voltage segment fiber is arranged in the high voltage equipment and fixed in a fiber channel in segment. The all-fiber current sensor suitable for the high voltage field can be installed in a DC converter valve of flexible DC transmission or a valve tower of high voltage equipment as a high-voltage DC breaker, can measure branch currents in the high voltage equipment, ensures effective current measurement without damage on the insulation performance of the high voltage equipment, and can satisfy certain mechanical strength requirement.