Using the daily averaged values of the F10.7 for years 1956-2003, the Morlet Wavelet Transform is used to analyze the characteristics of quasi-27-day period oscillation and the relation between the oscillation and the solar 11-year cycle （Schwabe cycle）. The result shows： The amplitude and period of quasi-27-day period oscillation have obvious short-term fluctuations. The change has very large difference in different years. In some years, the amplitude changes more than ten times and the period changes several days, even changes suddenly more than ten days during several days to tens of the day. In other years, the amplitude is large, but the fluctuation is small and the period was steady. The yearly averaged quasi-27-day oscillation amplitude has obvious change year after year and it is correlated with the solar 11-year cycle observably. Generally, the quasi-27-day oscillation amplitude is larger when yearly averaged F10.7 is bigger. But in the solar cycle 19 maximum years, the quasi-27-day oscillation amplitudes is smaller than maximum years of other cycles, although yearly averaged F10.7 of cycle 19 maximum years is bigger than other cycles. The quasi-27-day oscillation amplitude has obvious change year after year except some years （for example 1987）, and the yearly averaged period change range is 24-31 days and is not correlated with the solar cycle. The averaged period of 48 years is 27.3 days. On the whole, the period trends shorter gradually, the period decreases about 1.5 days during 1956-2003. The reasons that conduces to the fluctuations of quasi-27-day oscillation is very complicated, it needs to be studied in the future.
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