The present invention provides methods and systems for sequencing long nucleic acid fragment. The present invention also provides a method of sequencing a target polynucleotide with fewer probes. Further, the present invention provides a method of sequencing a target polynucleotide with longer reads. Locus-specific, ligation-assisted sequencing/genotyping method and ligation-captured sequencing method are also provided in the present invention. The methods of the present invention allow low-cost, high-throughput and accurate sequencing of nucleic acids.