The drag and the interia coefficients Cd,CM of wave-current force on vertical pile are well related to the redefined Keulegan-Carpenter number N'Kc by the test data of the authors. The relation could be also used for irregular wave-current force to calculate in time domain. A simplified method for the calculation of cumulative probabilistic distribution of peak value of irregular wave-current force is also recommended in this paper. These methods were justified by the model test of the authors.