Dengue fever is a contagious disease transmitted by Aedes aegypti mosquitoes. WHO reported that south east Asia and the western Pacific region bear nearly 75% of global dengue diseases. The dengue virus poses a global threat affecting 3.9 billion people in 128 countries with an estimated 2.1 million cases of DHF / DSS and 21,000 deaths per year worldwide. In 2015 there were 126,675 dengue cases recorded in 34 provinces in Indonesia, with 1,229 of them dying. The alpha-glucosidase enzyme is a valid antiviral target for enveloped viruses. Inhibition of ER alpha-glucosidase enzyme will interfere the maturation process and function of viral envelope glycoproteins. This inhibits the process of assembling virus particles and their secretions. Inhibition of ER alpha-glucosidase II enzyme is sufficient in antiviral activity of host cells against dengue fever in vitro and in vivo. Fragment-based drug discovery (FBDD) has become a tool for discovering drug leads. The approach first identifies fragments, tiny molecules, which are about half size of common drugs. The fragments are then linked together to generate drug leads. This research used ER alpha-glucosidase II enzyme with PDB ID 5IED. As much as 281 new compounds were developed computationally based on 3D structure of 5IED protein. After molecular docking simulations, toxicity tests, druglikeness tests, pharmacokinetic tests and protein-ligand interactions analyses, three best ligands were chosen namely LB.5 G2D, LO.1 G2D and LX.23 G2D. An LX.23 G2D molecular dynamics simulation showed that three amino acid residues played a very important role in ligand binding to 5IED protein. The amino acid residues were Asp451, Met565 and Asp640.