The singularities and oscillatory performance of Kelvin source Green’s function which consisted of a local disturbance part and a farfield wavelike part were analyzed and the relative numerical integral methods for the two parts were presented. A well behaved expression of local disturbance part was used to eliminate its singularities, and  an improved method based on trapezoidal integration rule was used to evaluate this part. Meanwhile, variable substitution with auxiliary technique such as local refinement of integral steps in narrow zones near false singularities was applied to calculate the farfield wavelike part function. According to the attenuation performance of the wavelike part, a finite upper limit of this part was employed to improve the efficiency. The numerical test results have proved the efficiency and accuracy of these integral methods. The methods can be applied to calculate wavemaking problem of floating structures in calm water.