Objective:To study the effect of 30-min nap at three low points of the rhythm during 40-hour sleep deprivation Method:Eight young subjects having normal sleep-wake habits were subjected to nap and total sleep deprivation conditions at an interval of 2 weeks The whole experiment was from 6:00 of the first day to 22:00 totally 40 hours The typing workload was given There were three times of naps, which lasted 30 min every time, at 13:00 (the first day), 1:00 and 13:00 (the second day) Visual event related potentials were measured at 1:00 and the end Symbol recognizing task was given before the experiment, after each nap, at the end of it, and two days after Results:In the symbols recognizing task, whether sleep deprivation with or without naps, the reactive time prolonged, the number of right decreased, the number of lose increased Compared with total sleep deprivation, the reactive time was shortened apparently while the number of right and lose did not change when naps were introduced Whether sleep deprivation with or without naps, the latency of P300 was prolonged, the number of right decreased while the amplitude did not change Compared with total sleep deprivation, the latency was shortened apparently while the number of right and amplitude did not change when having naps Conclusion:Nap has positive effects during sleep deprivation