Physiological meturity stage,kel water content in physiological maturity and natural drydown rate of 42 maize inbred lines and 8 hybrids were studied in field test.The results showed that the late and mid-late and mid-early inbred lines and hybrids tested reached their physiological maturity stage at 50～60 d and 45～50 d after silking,respectively,and at this time the water content of kel was 28%～42% and 26%～40%,respectively.The drydown rate of the inbred lines and hybrids tested had significant differences and had significant correlation with ear diameter and ear position.The late line Ji16,mid-late lines Ji846 and ZaC546,the mid-early line Longkang11 and the early line Dong91 were moisture quick-loss inbred lines and cound be used in fast drydown maize hybrid breeding program.