Abstract: Microwave remote plasma sources (RPS) leverage microwave energy within a resonant cavity to ignite plasma, which is separated from the process chamber, and exhibit distinct advantages, such as no electrode contamination and mitigating material surface bombardment by reactive particles. As a result, they are widely utilized in industries, including semiconductors and thin-film deposition. Traditional simulation and parameter optimization of the RPS focuses on modeling the electric field without plasma. This study proposes a parameter optimization approach for microwave RPS, exemplified by the discharge tube thickness, based on electric field simulations under ignition and operational conditions. To quantify the electric field distribution, multiple metrics are employed, drawing the conclusion that the optimal thickness is 5mm. Experimental validation with discharge tubes of various thicknesses further confirms the high consistency between the observed plasma luminous regions and simulation predictions, demonstrating the reliability and accuracy of the simulation method. The simulation and performance evaluation methodologies presented in this paper can be generalized for the design optimization of other parameters.