Ca3(BO3)2 crystal is a new stimulated Raman scattering (SRS) crystal applied in the UV region. However, its SRS-active mode has not been deeply studied. The Raman spectrum of the crystal was investigated by the density functional theory (DFT) calculation. All of the Raman-active modes were assigned, and the SRS-active mode was confirmed to be attributed to the fully symmetric vibration of the BO3-3 group. The SRS-active modes of the CaCO3 and Ca(NO3)2 crystals also arise from the fully symmetric vibrations of planar triangular groups (CO2-3 and NO-3), but their intensities are much higher than that of Ca3(BO3)2. Electron density analyses showed that the intensities of the SRS-active modes of the Ca3(BO3)2, CaCO3 and Ca(NO3)2 crystals are positively correlated with the electronic conjugation effects of the BO3-3, CO2-3, and NO-3 groups. The DFT calculation showed that the isotopic effect of boron is negligible on the line-width of the Ca3(BO3)2 SRS-active mode. When the pump laser propagates along the crystallographic aH or cH axes, the crystal Raman scattering cross sections are almost the same.