Check whether there are obvious multiple signal peaks to judge. If the possible sequence of the band is known, we can consider tapping and recycling, and then preliminarily judge whether the band is the desired product by enzyme digestion. If the sequence is unknown and the band length is short (100-200bp), we can consider using electrophoresis technology based on DNA conformational differences, such as SSCP. If the length is long, it can be determined by sequencing the purified PCR products and checking whether there are obvious multiple signal peaks.