Based on Khokhlov-Zabolotkaya-Kuznetsov (KZK) equation in frequency-domain, an approach to study the three-dimensional asymmetric nonlinear ultrasonic field is developed in this paper. The ultrasonic nonlinear field distribution behind the simulated rib-like barriers is investigated by numerical simulation and compared with the measured results. In addition, the influence of the barriers on the spatial-and-time-averaged intensity is discussed, which is helpful for future study on the HIFU treatment behind the ribs.