The probability distribution of in-line wave forces on a pile can bemathematically summed up to that of a theory and the assumption of wave period being constantare used and the above probability distribution is simplified to that of a single dimentsionfunction.The probability density functions of the peak values of total wave forces on a wholevertical pile in irregular waves are derived from that of wave height which is the Rayleighdistribution(deep water wave)or the Kerohovski distribution(shallow water waves)on the baseof the Morison Equation.The identification with experimental data shows that suchsimplification is successful.These distributions are compared with Weibull distribution andRayleigh distribution and the result shows that the shallow water distribution of wave forcesobtained here is the best one and can be used in practice. The probability distribution of in-line wave forces on a pile can bemathematically summed up to that of a theory and the assumption of wave period being constantare used and the probability distribution of which is one to a of dimentionfunction.The probability density functions of the peak values ​​of total wave forces on a whole ground in irregular waves are derived from that of wave height which is the Rayleigh distribution (deep water wave) or the Kerohovski distribution (shallow water waves) on the base of the Morison Equation. shows that suchsimplification is successful.These distributions are compared with Weibull distribution and Rayleigh distribution and the result shows that the shallow water distribution of wave forcesobtained here is the best one and can be used in practice.