The invention provides a design method for large blade roll forging dies on a 1600-mm roll forging machine. The first-pass roll forging die, the second-pass roll forging die and the third-pass roll forging die are included and are all closed type roll forging dies. The whole forming roll forging process has the characteristic that main change occurs in the roll forging forming process in the length and thickness directions of die cavities. The main functions of the first-pass roll forging die and the second-pass roll forging die in the roll forging forming process are to reduce the sectional area, so that a formed roll forged piece is drawn in the length direction. The main function of the third-pass roll forging die in the roll forging forming process is to enable the roll forged sectionto be almost close to the shape of a blade, namely the die forging forming function is achieved in the roll forging process, and roll forging upper die cavities and roll forging lower die cavities ofthe first pass, the second pass and the third pass are asymmetrical relative to the center line of a roll.