Mucins are large glycoproteins that cover and protect epithelial surface of the body. Gel-forming mucin domains of mucin genes are rich in proline, threonine, and serine that are heavily glycosylate. These domains show great complexity with tandem repeats (TRs), thus make it difficult to study the sequences. With the coming of single molecule real-time (SMRT) sequencing technologies, we manage to present sequence structure of mucin domains via SMRT long reads for gel-forming mucins MUC2, MUC5AC, MUC5B and MUC6. Our study shows that for different individuals, single nucleotide polymorphisms (SNPs) could be found in mucin domains of MUC2, MUC5AC, MUC5B and MUC6, while different number of tandem repeats could be found in mucin domains of MUC2 and MUC6. Furthermore, we get the sequence of MUC2, MUC5AC, and MUC5B mucin domain in a Chinese individual at accuracy of possibly maximum 99.98%, 99.93%, and 99.76%, respectively. We report a new method to obtain DNA sequence of gel-forming mucin domains. This method will provided new insights on getting the sequence for Tandem Repeat parts which locate in coding region. With the sequences we obtained with this method, we can give more information for people to study the sequences of gel-forming mucin domains.