Phospholipases A₂ (PLA₂) are interfacial active enzymes that catalyze hydrolysis at the sn-2 position of membrane phospholipids. In the catalytic active PLA₂ (D49 PLA₂), the Asp49 residue plays a key role in the coordination of the ion calcium that assists in the stabilization of the transition state intermediary. Despite the catalytic importance of Ca²⁺, it has low affinity for sPLA₂ active site. Molecular dynamics simulations of a D49 svPLA₂ from Agkistrodon halys pallas were performed in aqueous environment, methanol and octanol. Because of the svPLA₂ low affinity for the calcium ion in aqueous systems, different restrain forces were applied on Ca₂⁺ and evaluated with respect to ion coordination with key residues. All simulations were performed for a time period of 5 ns using the GROMACS package with GROMOS96 43a2 force field. The results have showed a series of important conformation changes of sPLA2v during its approaches to membrane surface, as the increase of the solvent accessible surface area and the reorientation of side chains of residues of catalytic importance. Analysis of the simulations data were utilized to propose a  interfacial activation model for svPLA₂. According, the principal events associated with svPLA₂ activation involve: a) the reorganization of calcium binding loop at membrane proximity followed by the of Ca²⁺ up take; b) side chain reorientation of Trp31, which will define a new specificity pocket for the phospholipid chain; c) reduction of the distance between His48 and Asp49, in order to increase the nucleophilicity of His48; d) side chain reorientation of Lys69 concomitant with the projection of 69-loop to solvent resulting in the increase of the active site accessibility. These results, in addition with knowledge biochemical and crystallographic data, open access to a more detailed understanding for the molecular mechanism associated with the interfacial activation of phospholipases A₂.