Conventional reverberation chamber has a rectangular structure including mode stirrers or mode-turned stirrers to obtain the field uniformity inside the chamber. This paper explained the way to improve the field uniformity in an asymmetric structure instead of conventional rectangular structure with right-angled planes. Two types of asymmetric structure were considered. One was an asymmetric reverberation chamber using Quadratic Residue Diffuser and the other was an asymmetric chamber with oblique enclosure including fixed Randomly Made Diffusers. The FDTD simulation method was used to analyze the field homogeneous characteristics of these asymmetric reverberation chambers.