3C 66A is one of our first batches of photometric monitoring objects with the 1 m optical telescope at Yunnan University Astronomical Observatory. In the present work, the observational campaign was performed from 2021 November 1 to 2022 February 27 in the Johnson–Morgan system V and R bands. The average magnitudes in each band were \(\bar{V}=15.52\pm0.18\) mag and \(\bar{R}=15.07\pm0.17\) mag. The overall variability amplitudes were \(\Delta V = 0.^{\rm m}74\), Amp = 70.27% and \(\Delta R = 0.^{\rm m}72\), Amp = 68.56%, respectively. Most of the intraday variabilities (IDVs) occurred in 2021 December and 2022 February. The minimal rise/decay timescale was about 6 minutes (5.82 ± 2.74 minutes and 6.18 ± 2.81 minutes on 2022 February 11, 6.99 ± 3.70 minutes and 6.17 ± 2.91 minutes on 2022 February 12). Durations of these rapid variabilities were from 11.99 to 179.67 minutes. The discrete correlation function analyses between V and R bands showed significantly correlated variability. Color index analysis of IDVs showed that the spectrums do not change with variabilities.