The invention relates to a method for determining the starting opportunity for emergency releasing of a deepwater drilling riser. The method comprises the following steps of determining a weak component and a releasing position D1 of an offshore drilling platform; determining a time point t1 when the drilling riser of the offshore drilling platform is released; determining time t2 for transmitting a surface wave-current load to the weak component; determining execution time t3 for completing the emergency releasing action of the offshore drilling platform and calculating a time point t1+t2-t3 after the offshore drilling platform drifts and the corresponding drifting distance D2 of the offshore drilling platform; determining a time point t4 for preparing releasing starting of the offshore drilling platform, calculating a time point t1+t2-t3-t4 after drifting of the offshore drilling platform and the corresponding drifting distance D3 of the offshore drilling platform, and calculating a time point t1-t4 after drifting of the offshore drilling platform and the corresponding drifting distance D4 of the offshore drilling platform; and finally determining the starting opportunity for releasing of the drilling riser of the offshore drilling platform.