Single nucleotide polymorphisms (SNPs) are closely related to genetic diseases, but current SNP detection methods, such as DNA microarrays that include tedious procedures and expensive, sophisticated instruments, are unable to perform rapid SNPs detection in clinical practice, especially for those multiple SNPs related to genetic diseases. In this study, we report a sensitive, low cost, and easy-to-use point-of-care testing (POCT) system formed by combining amplification refractory mutation system (ARMS) polymerase chain reaction with gold magnetic nanoparticles (GMNPs) and lateral flow assay (LFA) noted as the ARMS-LFA system, which allow us to use a uniform condition for multiple SNPs detection simultaneously. The genotyping results can be explained by a magnetic reader automatically or through visual interpretation according to the captured GMNPs probes on the test and control lines of the LFA device. The high sensitivity (the detection limit of 0.04 pg/μL with plasmid) and specificity of this testing system were found through genotyping seven pathogenic SNPs in phenylalanine hydroxylase gene ( PAH, the etiological factor of phenylketonuria). This system can also be applied in DNA quantification with a linear range from 0.02 to 2 pg/μL of plasmid. Furthermore, this ARMS-LFA system was applied to clinical trials for screening the seven pathogenic SNPs in PAH of 23 families including 69 individuals. The concordance rate of the genotyping results detected by the ARMS-LFA system was up to 97.8% compared with the DNA sequencing results. This method is a very promising POCT in the detection of multiple SNPs caused by genetic diseases.