A large-scale molecular dynamics simulation was carried out in order to investigate the adsorption mechanism of ribosomal protein L2 (RPL2) onto a silica surface at various pH values, RPL2 is a constituent protein of the 50S large ribosomal subunit, and a recent experimental report showed that it adsorbs strongly to silica surfaces and that it can be used to immobilize proteins on silica surfaces. The simulation results show that RPL2, especially domains I (residues 1-60) and 3 (residues 203-273), adsorbed more tightly to the silica surface above 7. We found that a major driving force for the adsorption of RPL2 onto the silica surface is the electrostatic interaction and that the structural flexibility of domains 1 and 3 may further contribute to the high affinity.