This paper is focused on the design of a printed slot antenna with multiple-notch function for ultra-wideband applications, accompanied with enhanced gain for Compass Naviga- tion Satellite Systems. The proposed antenna consists of a curved radiation patch with an arc gradient microstrip line configuration and a class octagonal-shaped wide slot on a rectangular ground plane, supporting a much wider impedance bandwidth. With a class C-shaped slot on the patch and a class L-shaped strip attached on the ground, the multiple-notch function could be achieved to cover all of the 5.2/5.8 GHz WLAN, 3.5 GHz WiMAX and 4 GHz C-bands. By introducing a third-order stepping strip at the upper part of the wide slot on the ground, an additional operating frequency at 2.492 GHz of CNSS band can also be realized. The simulation results show that the designed antenna is with a small size and relative bandwidth larger than 122% in the band of 3.10 ∼ 12.99 GHz. The radiation patterns and current distributions are also analyzed respectively for the performance improvement.