Body surface backed single and multiple notch antennas for 17 GHz on body wireless sensor communications are presented in this paper. The proposed antennas are designed to excite both body surface wave propagations and off body radiations, which are strictly required by wireless body area networks (WBAN) sensor communications. To realize those propagations and radiations, human body surface is utilized as a reflector for the antennas. The presented antennas fabricated on 100 um thick polyimide flexible laminates are numerically and experimentally studied both in free space and on real body surface, and the body effects on antenna impedance and radiation performance are also analyzed. Good agreements between simulations and measurements are achieved. It is shown that the proposed antennas feature about 10% impedance bandwidth (S11 = -10 dB) and higher than 3.7 dBi gain in free space. The antenna resonant frequencies are slightly detuned and the antenna gain is increased when they are placed close to body surface. Moreover, the surface wave propagations and radiations off body surface are also investigated by measuring transmissions between two identical single and multiple notch antennas on body surface, respectively.