Abstract: The compressional-wave velocities (Vp) and shear-wave velocities (Vab and Vav )of early Paleozoic S-type and I-type granitoid samples collected from the central and west part of Guangdong province were measured accurately both at atmospheric pressure and room temperature and during heating (up to 1 05℃ )and pressuring (up to 5. 06 × 1 0 7 Pa). Through systematic calculation, we obtained the average values of wave velocities (Vp,Vab an d Vav ),the ratio of compressional-wave velocities and shear-wave velocities (Vp／Vab)and Poisson’s ratio under atmospheric pressure and room temperature and the curves of P-wave and S-wave veloities at various pressures and temperatures. The values of wave velocities(V p,Vab and Vav),Vp／Vab and Poisson’s ratio are different obviously between S-typ e and I-type Granitoids. The average values of wave velocities(Vp, Vab and Vav), Vp／Vab and Poisson’s ratio of S-type granitoids are 5005m／s,2897m／s,2591m/s and 0. 25 and smaller than those of I-type granitoids (5512m／s,2937m／s,2671m／s and 0. 30) especially in compressional-wave velocities. the difference is 507m／s and is 1 0 of wave velocity value of S-type granitoids. The values of Vp／Vab for S-type and I-type granitoids are larger than 1. 70 and located in the normal range of granitoids, but the values of I-type granitoids are larger than that of S-type granitoids. The values of wave velocities of S-type and I-type granitoids increase gradually with increasing pressure and decrease gradually with increasing temperature, but the range of S-type granitoids is larger than that of I-type granitoids obviously. The anisotropy of S-type granitoids is up to 1.10 and larger than that of I-type granitoids. From the elastic properties of S-type and I-type granitoids, we can conclude that the structure and porosity in S-type granitoids are better developed than those in I-type granitoids, and the granite body was intensely compressed in the direction of NNW-SSE during the process of formation.