The effects of R0,m and TR2,m acoustic modes of guided acoustic wave Brillouin scattering on gain, phase modulation and additional birefringence in single mode fiber were investigated by the all-vector finite element method. The results show that the gain of guided acoustic wave Brillouin scattering reaches maximum at their frequencies matching those of R0, 8 and TR2, 10 modes in R0, m and TR2,m (0°/90°) mode, and the gain increases with the increasing of pump power. The Stokes wave phases modulated obviously by R0,1, TR2,5, TR2,7 and TR2,10 modes, where TR2, m mode plays a vital role in the phase modulation which linearly increases with the increasing of pump power. TR2,1,TR2,5,TR2,7,TR2,10 modes obviously induce additional birefringence which linearly increase with pump power increasing.