The Phred quality score can measure the sequence quality, and quality scores are normally stored together with the nucleotide sequence in the widely accepted FASTQ format. For sequence raw reads with various FASTQ formats, the range of scores will depend on the technology and the base caller used. With the different technology, the range of scores is different. For learning the comparing and converting method of sequence Phred quality score, we do an experiment, and analyze the different between various FASTQ quality formats.