Abstract: The paper presents the results of the numerical investigations of the finite amplitude waves interaction problem for circular piston with Gaussian pressure amplitude. The mathematical model and some results of numerical investigations are presented. The mathematical model was built on the basis on the Khokhlov – Zabolotskaya – Kuznetsov equation (KZK equation). To solve the problem the finite-difference method was applied. The on-axis pressure amplitude as a function of distance from the source for different frequency waves and their pressure amplitude distributions at horizontal section were investigated. The calculations were done for different values of source and medium parameters. The results of computer calculations were compared with analytical solutions of the KZK equation in special cases.