Abstract: Rubisco (Ribulose 1,5-bisphosphate Carboxylase / Oxygenase) is the first key enzyme in the photosynthesis pathway. In this study, the full length cDNA, encoding Rubisco large subunit (RbsL) was cloned from Ulva linza for the first time. Partial rbcL cDNA sequence of 1 101 bp was first cloned by RT-PCR from total RNA, then, both sequences at 3′ and 5′ ends were amplified using 3′ -RACE and 5′ -RACE technologies that yielded 579 bp and 371 bp DNA fragments respectively. A full length cDNA sequence of 1472 bp was obtained from these cloned sequences and was assigned to a new NCBI accession number DQ813496. It contained the 1 425 bp full coding sequence for Rubisco large subunit (RbsL) and a leader sequence of 47 bp, and it encoded a protein of 474 amino acids. Through bioinformatic analysis and BLAST search, the full cDNA sequence in Ulva linza showed high homologies to known full length cDNAs of the same gene from other green algae where rbcL cDNAs were previously cloned. The identity ranged from 82.07% to 85.78%, and 88.00% to 94.11%, respectively, at DNA and amino acid levels. The highest homology of the protein was obtained between Ulva linza and Chlorella pyrenoidosa. Based on the newly identified cDNA sequence, multiple alignment was performed by using bioinformatic software among amino acid sequences of Ulva linza and other two higher plants and one green alga. Then, the secondary and three-dimensional structures for Rubisco large subunit in Ulva linza were also predicted and analyzed with online programs.