This paper presents a broadband continuous transverse stub (CTS) antenna array with wide scanning range based on substrate integrated waveguide (SIW). The SIWCTSs radiators are periodically arranged on the coplanar waveguide (CPW). A novel broadband CPW slowwave structure is proposed as the feedline to increase the phase difference of the adjacent antenna elements. Depending the phase variation from 89.3° to -83.3° within the frequency range of 8.6~13.7 GHz, a wide beam steering range depending on frequency is achieved. A reflector is located at onefourth wavelength away from the antenna array to reduce the backward radiation. A 4element CPWCTS antenna array based on SIW is designed and simulated using the HFSS fullwave analysis software. The simulated results show that the frequency range of the reflection coefficient less than -10 dB is 8.6~14 GHz. The main beam of the antenna is scanned from -40° to 56° in Eplane with the frequency increasing. At every main radiation direction, the gain varies within the range of 9.8 ~ 12.3 dBi.