In order to study the lateral resistance of reinforced traditional Chinese timber frames with mortise-tenon connections, three cyclic tests were conducted on one-bay mortise-tenon jointed traditional timber frames. Three reinforcement methods, i.e., steel angle strengthening, wood brace, and Timu, were studied. Seismic performances were evaluated according to the experimental phenomena and the test results. The failure mode, hysteresis curves, skeleton curves, curves of stiffness degradation, and energy dissipation capacity of the three specimens were analyzed based on the tests. The test results showed that the wood frames had good deformability. The stiffness degradation of the timber frame was severe at the initial loading stage; however, the degradation rate tended to decrease after the initial stage. In addition, the energy dissipation increased as the lateral displacement increased. The wooden frames with mortise tenon joints strengthened by steel angle, wood brace, and Timu can achieve good aseismic results. The study can provide a theoretical basis for seismic design and reinforcing methods of traditional timber structures.