Abstract: Tension is the key factor in the safe operation of deepwater drilling riser systems, especially for the safe operation of emergency disconnection of the riser system. However, the present calculation methods of the top tension of drilling riser system (including the API theoretical method, a method based on the residual tension at bottom of the drilling riser system and a method based on the maximal hook load during drilling riser system running procedure) do not take riser recoil response into consideration. To address the issue, the tension design criteria based on the riser recoil response was determined. The modified API top tension calculation method and process were proposed and then verified by examples. The results showed that the modified API algorithm could provide reasonable tension calculation for riser systems. The LMRP displacement, the stroke of tensioner and fluctuation range of the effective tension during riser recoil were reduced, thus improving the security of drilling riser system after emergency disconnection and ensuring a safe deepwater drilling riser system emergency disconnection operation.