Microcrystalline silicon thin films with and without a seed layer were deposited using very high frequency plasma enhanced chemical vapor deposition method at a high growth rate. The influence of the seed-layer method on the film growth and structure were investigated using spectroscopic ellipsometry(SE), Raman spectrum and X-ray diffraction. The results show that the seed-layer can not only increase the growth rate, but also promote crystalline nucleation at the initial growth stage. The deposition processes were monitored by real time spectroscopic ellipsometry(RTSE). The film was also measured by ex situ SE in the air. The differences between the RTSE and ex situ SE have been studied in testsing the microcrystalline silicon thin films. Results show that for the thin films the total thickness obtained by RTSE is smaller than that by ex situ SE, while for the thick films the measured total thicknesses by two methods are almost the same. However, the surface roughness thickness detected by RTSE is larger than that by ex situ SE. The reason for this is due to oxidation of the thin film exposed to the air which smoothed the film surface.