  We reported the result of long term optical variability of the blazar 4C
29.45 (QSO 1156+295, Ton 599), carried out optical photometric observations in
Johnson V, Cousins RI passbands during April 1997 to March 2002 using the 1.56
meter telescope of the Shanghai Astronomical Observatory (SHAO) at Sheshan,
China, compiled the post-1974 optical photometric data of the blazar by
combining our new observations with the published optical data, and found
maximum variations in different passbands: $\Delta$U = 4.41 mag, $\Delta$B =
5.55 mag, $\Delta$V = 4.53 mag, $\Delta$R = 5.80 mag, and $\Delta$I = 5.34 mag.
The average color indices are: U$-$B = $-0.54\pm$0.18 mag, B$-$V =
0.56$\pm$0.21 mag, B$-$R = 0.93$\pm$0.18 mag, B$-$I = 1.51$\pm$0.24 mag, V$-$R
= 0.44$\pm$0.15 mag and V$-$I = 1.03$\pm$0.23 mag. The post-1974 data give us
an excellent opportunity to search for the existence of possible periodicity in
the light curve. In search for periodicity in the R passband light curve, we
performed Jurkevich test and power spectral (Fourier) analysis methods, and
CLEANest algorithms to remove false signals. We found possible periods of 3.55
and 1.58 years. The possible mechanism for the periodic variability was
discussed.
