  3C 66A was monitored by the BATC(Beijing-Arizona-Taipei-Connecticut)
telescope from 2005 to 2008,1994 observations were obtained on 89 nights.
Detailed research and analysis was performed on these observations in this
paper. A long term burst occurred in the whole light curve. No intra-day
variability was claimed in our campaign by intra-night light curve analysis.
Time lag of shorter wavelenth preceding longer wavelength was shown by
correlation analysis. The results showed that the optical spectral shape turned
flatter when the source brightened, and the spectral variability indicator was
bigger on shorter time-scale as determined by the color indices variation
analysis.
