Interferences due to the hostile environment (e.g. jammer) and the multi-user access are critical factors affecting performance of the wireless sensor networks. In this paper, we study a hybrid frequency hopping/time hopping-pulse position modulated (FH/TH-PPM) UWB for wireless sensor networks in hostile environment with partial-band (PB) tone interference. FH and TH are both used to get as much diversity gain as possible. Theoretical analysis is made for the bit error rates performance in the presence of multitone/pulse (tone in frequency domain and pulse in time domain) interference and multi-user interference. We also derived theoretical performance formula when the low duty-cycle in UWB system and the large number of sensor nodes in a wireless sensor networks are considered