Rock masses are distinguished from other engineering materials by the existence of joints. When a wave propagates through a rock mass, it is significantly attenuated due to the reflection and dissipation at joints. Great efforts have been made to study the effects of joints on wave propagation in the past. However, there still exist remaining problems. For example, limitation exists in previous methods in studying wave propagation across multiple joints; few studies have been conducted for wave propagation across filled joints and across multiple intersecting joint sets. Focused on the remaining problems, wave propagation in jointed rock masses is theoretically and numerically studied in this thesis. In order to study the effects of multiple joints on wave propagation, one method termed the virtual wave source method (VWSM) is introduced, and the existing recursive method (RM) is modified. Both of the newly introduced method and the modified method overcome the limitations of previous methods. The displacement and stress discontinuity model (DSDM) is introduced to approximately describe the physical properties of viscoelastic filled joints as boundary conditions in the wave equations. Other than the displacement discontinuity model (DDM), the DSDM is more appropriate in studying the effects of filled joints on wave propagation. With the VWSM, wave propagation across a non-filled joint set is theoretically studied. For normally incident wave across joints, an interesting phenomenon that the amplitude of transmitted wave increases with increasing number of joints is observed and explained. The complete solutions for obliquely incident wave propagation across a single non-filled joint described by the DDM are derived through plane wave analysis. Parametric studies are also performed for obliquely incident wave propagation across a single joint and multiple parallel non-filled joints. In addition to non-filled joints, the effects of filled joints on wave propagation are also studied. The filled joint can be modeled by the accurate yet complicated continuous model, i.e., the layered medium model (LMM), and the simple yet approximated discontinuous model, i.e., the DSDM. With the modified recursive method (MRM), wave propagation across a single joint and multiple parallel joints filled with viscoelastic medium is studied based on the continuous model. The results are compared with wave propagation across joints filled with elastic medium. With the DSDM, the complete solutions for obliquely incident wave across a single viscoelastic filled joint are derived and verified with experimental data. Parametric studies on wave propagation across a single filled joint and multiple parallel filled joints are also conducted. Universal distinct element code (UDEC) is used to study wave propagation across multiple intersecting joint sets in rock masses. The capability of UDEC on modeling wave propagation across joints is verified through comparison with theoretical solutions. Extensive parametric studies on wave propagation across multiple joint sets are subsequently performed.