A multi-turn absolute encoder, comprising a rotary shaft, wherein the multi-turn absolute encoder further comprises: a control circuit board, having a first side and a second side, the first side of which faces the end of the rotary shaft orthogonally to the principle axis of the rotary shaft; a magnet, disposed on the first side of the control circuit board, connected to an end of the rotary shaft proximal to the control circuit board, and configured to synchronously rotate about the rotary shaft; a Hall sensor, disposed at a position corresponding to the magnet on the second side of the control circuit board, and configured to acquire turn count information of the rotary shaft upon power interruption; a controller, disposed on the control circuit board, electrically connected to the Hall sensor, and configured to acquire data of the Hall sensor upon power interruption, wherein the controller is adapted to be supplied with power from a battery to power the Hall sensor; a primary controller, disposed on the control circuit board, and electrically connected to the controller; a single-turn absolute encoder, disposed at a position in the axial direction of the shaft and proximal to the magnet on the first side of the control circuit board, electrically connected to the primary controller, and configured to acquire magnetic information relating to the absolute angular position within a single turn of the rotary shaft upon power on; and a non-volatile memory, disposed on the control circuit board, electrically connected to the primary controller, and configured to, in power interruption, store absolute position information of the rotary shaft calculated by the primary controller prior to power interruption; wherein the primary controller is configured to calculate the absolute position information of the rotary shaft based on the turn count information of the rotary shaft, the magnetic information relating to the absolute angular position within a single turn of the rotary shaft and the absolute position information of the rotary shaft stored in previous power interruption. a control circuit board, having a first side and a second side, the first side of which faces the end of the rotary shaft orthogonally to the principle axis of the rotary shaft; a magnet, disposed on the first side of the control circuit board, connected to an end of the rotary shaft proximal to the control circuit board, and configured to synchronously rotate about the rotary shaft; a Hall sensor, disposed at a position corresponding to the magnet on the second side of the control circuit board, and configured to acquire turn count information of the rotary shaft upon power interruption; a controller, disposed on the control circuit board, electrically connected to the Hall sensor, and configured to acquire data of the Hall sensor upon power interruption, wherein the controller is adapted to be supplied with power from a battery to power the Hall sensor; a primary controller, disposed on the control circuit board, and electrically connected to the controller; a single-turn absolute encoder, disposed at a position in the axial direction of the shaft and proximal to the magnet on the first side of the control circuit board, electrically connected to the primary controller, and configured to acquire magnetic information relating to the absolute angular position within a single turn of the rotary shaft upon power on; and a non-volatile memory, disposed on the control circuit board, electrically connected to the primary controller, and configured to, in power interruption, store absolute position information of the rotary shaft calculated by the primary controller prior to power interruption; wherein the primary controller is configured to calculate the absolute position information of the rotary shaft based on the turn count information of the rotary shaft, the magnetic information relating to the absolute angular position within a single turn of the rotary shaft and the absolute position information of the rotary shaft stored in previous power interruption.