Abstract: The finite amplitude wave propagation problem for circular source was considered. The paper presents mathematical model and some results of theoretical investigations. The problem was considered as an axial symmetric one. The mathematical model was built on the basis of the Khokhlov – Zabolotskaya – Kuznetsov (KZK) equation. To solve this equation the Fourier series expansion and finite-difference method were applied. The pressure harmonic amplitudes as a function of distance form the source and waveform were examined. Influence of discrete model parameters on accuracy of numerical calculations was investigated.