A heat treatment technology for an R6 level mooring cable comprises the following steps that firstly, a mooring cable chain enters a quenching furnace barrel to be preheated; secondly, the mooring cable chain enters a rapid heating area; thirdly, the temperature of the mooring cable chain in a quenching temperature heating area is controlled to be at 1,045 DEG C, after the mooring cable chain enters an insulating area, the temperature is controlled at 1,015 DEG C and kept for 190 min, then water cooling is conducted, and the running speed of the chain during quenching is 0.19 m / min; fourthly, the mooring cable chain enters a tempering furnace barrel and then is preheated; and fifthly, the mooring cable chain enters a heating area; sixthly, the temperature of the mooring cable chain in a tempering temperature heating area is controlled at 690 DEG C, after the mooring cable chain enters the insulating area, the temperature is controlled at 640 DEG C and kept for 190 min, and then water cooling is conducted again. According to the heat treatment technology, expected material inner structure transformation of the chain can be achieved; and good economic and social benefits are achieved for application and popularization.