Magnesium Sulfate solution is an important electrolyte solution which is widely used in many fields. The characteristics and the association equilibrium of Mg2+ and SO42- have been the focus of attention, which has important application values. In this paper, the characteristic of ion association structure of Mg2+ and SO42- in different concentration MgSO4 solutions at different temperature were studied by Raman Spectroscopy combined with Gauss-lorentz peak fitting program. Furthermore, the ion association equilibrium constant KR of MgSO4 solutions were calculated. Furthermore, the apparent thermodynamic parameters of the associated reaction of Mg2+ and SO42? and the product of the contact ion pair CIP′under standard state were inferred. The spectra experiments results showed that the peak area and peak intensity of the ν1-SO42? characteristic peaks in MgSO4 solution were linearly associated with the concentration of SO42?. The free SO42- ion was the main structure of ν1-SO42? characteristic peaks. During the process of the temperature increasing for high concentration of 1.5mol/L and 2.0mol/L MgSO4 solution, the peak area and peak intensity of the ν1-SO42? characteristic peaks decreased, red shift phenomenon occurred in the peak position, and the symmetry of the peak changed. Accordingly, the content of free SO42- ions decreased, the chance of monodentate contact ion pairs (CIPs) increased, but the content of bidentate CIPs and SO42- groups structure changed irregularly. Likewise, the ion association equilibrium constant KR of MgSO4 solution increased which showed that the ion association equilibrium moved to the right with the temperature increasing for 1.5mol/L and 2.0mol/L MgSO4 solution, thus more CIPs generated. In dilute MgSO4 solutions, there were almost no bidentate CIPs and SO42- groups structure detected, the ion association structure of ν1-SO42? characteristic peaks and KR value changed irregularly. At the same temperature, the KR value decreased exponentially with the increasing of the concentration of MgSO4 solution.