An efficient geometric optics (GO) method is successfully developed for the field uniformity (FU) analysis and converted to an in-house computer-aided design (CAD) software tool for anechoic chamber design. It can help anechoic chamber companies to select the right radio absorbing materials for a chamber to meet the desired specs. Simulation and measurement results are obtained and compared, and good agreement is obtained. It is shown that this method is accurate and efficient for chamber simulation, especially at high frequencies.