We investigate fractional quantum Hall effect at finite temperature using a fermion Chern-Simons field theoretical approach. In the absence of impurity scattering, the essential aspects of fractional quantum Hall effect, such as the quantization of Hall conductance, as well as quasi-particle charge and statistics are unrenormalized by thermal fluctuations. On the other hand, we find that the low energy excitation spectrum at finite $T$ may undergo some qualitative changes as temperature raises. Possible experimental consequences are discussed.

12 pages, Revtex (3 figures will be sent through airmail upon request)