  The star CQ Tau belongs to the family of UX Ori type stars. It has very
complex photometric behavior and complex structure of the circumstellar
environment. In our paper we constructed the historical 125 years light curve
of this star basing on the published photometric observations. It follows that
besides a random component characteristic of UX Ori type stars, the large
amplitude periodic component with the 10 year period is also present. Its
existence was suspected earlier in [11]. New observations confirm its reality.
It points to an existence of the second component close to the star. The
density waves and matter flows caused by the companion motion lead to periodic
changes in the circumstellar extinction and brightness of the star. This result
is discussed in context of the recent observations of CQ Tau with high angular
resolution.
