An assistant intracardiac positioning device for ligaturing and closing the left aurcle through an epicardium at the lower part comprises a positioner and a ligaturing device, and is characterized in that a profile of the positioner is in a rose bud shape; a groove structure is arranged close to the bottom of the positioner; the positioner is formed by spacing a plurality of self-swelling shape memory nickel-titanium alloy wires; the positioner is loaded into a catheter for conveying after the bottom is connected with an operation rod; and after the positioner leaves the catheter, the positioner swells automatically and restores to be in the rose bud shape. According to the assistant intracardiac positioning device, an additional device is not required to be implanted into a heart chamber; after ligaturing, no residual cavities or residual leakages are left; and risks of thrombi and cardiac tamponade are low. The device is convenient to operate, and can reduce operation risks, shorten the operation time and improve the operation success rate.