A novel leaky-wave antenna (LWA) utilizing spoof surface plasmon polaritons (SSPPs) excitation is proposed with continuous scanning range from endfire to forward. The designed transmission line unit supports two SSPPS modes, of which the 2nd order mode is applied in the design. A novel strategy has been devised to excite the spatial radiation of the –1st order harmonics by arranging periodic counter changed sinusoidal structures on both sides of the SSPPs transmission line. Both full-wave simulation and measurement results show that the proposed LWA presents wide scanning angle from endfire to forward. In the frequency range from 4 GHz to 10 GHz, LWAs achieve scanning from 90° to +20°, covering the entire backward quadrant continuously.