This paper presents a practical design method for the critical-conduction mode power factor correction (CRM PFC) converter by using an interactive mathematical computation and documentation software, the MathCAD. Many design factors affect the performance of a switching converter from the point view of efficiency optimization or dynamic response. The design of a CRM PFC converter is an involved process and there is a need for practical design engineers to follow an interactive and intuitive design procedure. This paper presents a suggested design procedure for line current total harmonic distortion (THD) reduction and loss analysis of the CRM PFC converter in considerations of practical design limitations. An illustrated design procedure is presented with given design example by using the MathCAD. Computer simulations have been carried out by using power electronic system simulation software, the PSIM, to verify the design results.