The invention provides a full scale fatigue test method of a deep water steel catenary riser. The full scale fatigue test method comprises the steps of 1, preparing a test sample; 2, preparing a test;3, loading the test sample; 4, starting the fatigue test; 5, setting a fatigue test acceptation standard; and 6, analyzing the test by using the test sample fracture. The method can evaluate the effectiveness and reliability of the fatigue performance of the welding technology, can verify whether the fatigue performance of the welding technology reaches to the welding specification requirements of the deep water steel catenary riser and provides a technological base for welding of the deep water steel catenary riser.