Abstract: A calculation of pressure distribution on rotor blades with three-dimensional nonsteady theory of compressible fluid is presented in the case of continuous wake-surface and forward motion of a helicopter at a constant speed. An acceleration potential equation is derived. A fundamental solution of the pressure doublet in an arbitrary motion is given. In order to satisfy the wake condition it is assumed that the pressure doublets move along the wake surface instead of along the actual tracks of blades. By adding the moving pressure doublets, an integral equation of the three-dimensional non-steady compressible fluid with superior singularity is obtained when the blades are in complex motion. The significant effect of compressibility on the higher harmonic pressures is shown in this equation. The kernel function for the integral equation is divided into two parts: one with superior singularity and a continuous function with a strong peak. For the former the Hadamard principal value can be determined as for a wing. With the aid of a proper spline function procedure the function ein is separated from the function, hence it becomes possible to calculate the higher harmonic pressures. A simple typical example is completed on a small computer to justify the equation and the method.