Taken J-Lay type pipe-laying vessel operation in 3 000 m deepwater as research object, the full coupled numerical analysis model is established. Through quasi-static analysis, the variation of riser sensitivity parameters is studied, and the optimal top inclination angle of the riser in pipe-laying operation is determined. Considering the combined action of current, wind and wave, the operation process in different conditions are simulated. The mechanical character and motion state of the top fixed point of the riser are predicted and studied. The results indicate that the variation of the riser top inclination angle is of obvious influence on the maximal bending moment of the riser, and the top inclination range is suitable in the range from 80° to 85°. In the combined action of wind, wave and current, as the coupling action of rolling and pitching motion, the maximal bending moment of the top of the riser sharply increases in beam wave and stern wave, which should be paid more attention to.