The invention discloses a safety device of a linear cutting anastomat for surgery. The safety device is provided with a nail box arm (3); the front part of the nail box arm is provided with a nail box (6), while the rear part is provided with a push cutter rod (7) capable of pushing a cuter (8) to move forward along a nail box cutting slot (62); the nail box arm is provided with a safety mechanism (9), and the safety mechanism is provided with a first elastic component (93) for elastically supporting the front part of the push cutter rod (7) and a safety block protrusion (94) downwards extending into an upper edge slot (72) of the supported push cutter rod; the cuter (8) forwards extends into the cutting slot (62) of the nail box (6); the supported front part of the push cutter rod is upwards acted on a safety bolt (61) which is blocked at the rear port of the nail box cutting slot and can be pushed forwards to support the rear end of the nail box; and the safety mechanism is also provided with a second elastic component (92) which is blocked at the front lower part of the supported push cutter rod and can be pressed down by the nail box. The safety device has the advantages of high safety factor, easy operation and simple structure, and can effectively avoid error operation of instruments.