The encoding structures of on-off keying (OOK), pulse position modulation (PPM), differential pulse position modulation (DPPM) and digital pulse interval modulation (DPIM) are analyzed in detail. And modulation modes are simulated and compared from bandwidth requirements, average transmission power, transmission capacity and error performance. The results show that DPIM has higher transmission capacity, less bandwidth requirements, lower synchronous requirements at the condition of demodulating and easier to be realized comparing with PPM. And with UV LED array, it will be the development trends of applicable UV light source. DPIM has more advantages?in the?application of?UV communication system?in the future.