The invention relates to method for a synchronous detection of sweet potato feathery mottle virus (SPFMV), sweet potato virus C (SPVC), sweet potato virus G (SPVG) and sweet potato virus 2 (SPV2), and belongs to the field of plant protection. The method comprises the following steps of respectively designing and synthesizing specific forward primers and a universal reverse primer of SPFMV, SPVC, SPVG and SPV2, extracting total RNA of tissue of a diseased plant through a cetyltrimethyl ammonium bromide (CTAB) method, and carrying out one step quadruplex reverse transcription-polymerase chain reaction (RT-PCR) magnification process to realize a synchronous detection of SPFMV, SPVC, SPVG and SPV2. Primers designed by the method have strong singularities and SPFMV, SPVC, SPVG and SPV2 share areverse primer thus an interaction of primers is reduced. In the invention, a CTAB method is utilized for extracting RNA from tissue of an RNA virus infected plant, thus a quality of RNA is guaranteed and a detection cost is reduced effectively; and the inverse transcription and the multiple PCR are completed in one step thus a detection time is saved. The method has the advantages of rapid detection speed, high efficiency, strong singularity, high sensitivity and low cost and can realize a synchronous detection of four kinds of sweet potato virus thus has wide application prospects.