In order to solve the severely ill-posed Cauchy problem of 3D Helmholtz-type equation, a modified kernel method based on exact solution is proposed. By constructing a mollification operator, the ill-posed problem is transformed into a well-posed problem, and stable numerical approximation solutions are obtained. When the wave-number $k$ and parameter $m$ meet the necessary conditions, the error estimates between the regularization approximation solution and exact solution are given in terms of $L^2$-estimate and $H^s$-estimate under the suitable choices of the regularization parameter. The theoretical part is verified by numerical examples. The results show that the proposed regularization method is stable and effective.