Abstract: Based on the regional harvest reports of Ching Dynasty kept in the Palace Museum in Beijing and recent records,a series of harvest records of winter wheat during 1736-1978 over Beijing area was constructed.The harvest were presented as a percent of full harvest.Harvest records were spectrally analysed to obtain significant periods of oscillation.It may be seen that there exist 121,80-years and other periods.1744(27% of full harvest) was the worst harvest since 1736.As concerns decade means,1921-1930(56%),1741-1750(60%) were the two worst and 1801一1810(80%) was the best.