The invention discloses a mechanical logic control bidirectional actuating mechanism based on shape memory alloy, which is characterized in that a magnet spring mechanism is adopted to replace the traditional electronic control system to realize sequential control of antagonistic shape memory alloy spring alternate actuation; two sets of antagonistic shape memory alloy are arranged on two sides ofa sliding block respectively and drive the sliding block to move in a reciprocating mode; the magnet spring mechanism is composed of three magnets and two extension springs, two of the magnets are connected with the extension springs located at two ends of the actuating mechanism, and the other magnet is connected with the sliding block; during the sliding motion, the sliding block magnet is alternately attracted and disconnected with the spring magnets on the two sides, and thus the shape memory alloy spring set is alternately powered on and off. In order to ensure that the shape memory alloy spring set is powered on and powered off at the same position in each working cycle, a pre-strain flexible bistable structure is introduced; and two steady-state positions are set as power-on positions by utilizing the characteristic that the energy of the bistable mechanism is the lowest at the steady-state positions, so that the reliability of the sliding block reaching the power-on and power-off positions is improved.