In this paper, an improved method ^[1] for the chemical synthesis of ^2SeU-RNA was reported using a streamlined strategy employs 2'-O-Thiomopholine-4-carbothioate protecting group. And single step deprotection of the resulting oligoribonucleotide product using 1,2-diamines/toluene under anhydrous conditions would retain the Selenium atom introduced on the 2-possiton of the modified Uracil. The process is doable with most standard heterobase protection and deprotection, it greatly simplifies the synthesis of ^2SeU-RNAs and can be applied to other Selenium modified RNAs synthesis. It makes the synthesis of RNA become as simple and efficient as the chemical synthesis of DNA. Furthermore, the design and synthesis of self-assembling ^2SeU-RNA square are reported which enable further structure studies and application of unique ^2SeU-RNAs.