This paper presents an optimal weighting factor (OWF) selection algorithm for the variance-reduced partial parallel interference cancellation (VRPPIC) technique proposed by Wang and Wu in multicarrier code division multiple access systems. In this approach, a monotonically increasing conditional variance function of weighting factors derived from the VRPPIC operations is minimized under a system loading constraint so that the OWFs can be easily obtained. Simulation results show that the proposed algorithm can effectively enhance the system performance.