Determining the functional impacts of disease-causing genetic variants presents consistent challenges in the genetic disease field. Here, we present a protocol for implementing saturation mutagenesis-reinforced functional assays to generate functional scores for small-sized variants in disease-related genes. We describe procedures for nucleofection to establish cell line platforms, programmed allelic series with common procedures (PALS-C) cloning for saturation mutagenesis, fluorescence-based cell sorting, next-generation sequencing, and functional score generation. This framework holds potential for high-throughput and cost-effective interpretation of unresolved variants in a broad array of disease genes. For complete details on the use and execution of this protocol, please refer to Ma et al.1.