Abstract：This paper presents a design of an improved signal structure of Chaotic Pulse Position Modulation(CPPM), in view of the fact that the chaotic sequence will lost its chaotic characteristics in the traditional CPPM-UWB system. The performance of the improved chaotic pulse position modulation Ultra Wideband (UWB) communication system is analyzed under the condition without Inter Symbol Interference(ISI), when the system uses Rake receiver of IEEE UWB indoor multipath channel model. The simulation of bit error rate for different Rake receivers on the indoor multipath environment is carried out. The studies indicate that the choice of the number of pulses per bit, the distance between the receiver and the transmitter and the average pulse repetition period have a great influence on system BER. The Rake receiver in the CM1 channel enjoys the best performance under IEEE UWB indoor multipath channel. The computer simulation shows that the performance of ideal Rake receiver is the best though its system is the most complicated. It is also shown that the performance of PRake receiver is better than SRake's and its system is also more complicated than SRake's. The performance of SRake and PRake receivers is improved significantly with the increase of interdigitated number.