The CCD photometric data of the EW-type binary , II CMa , which is a contact star in the field of the middle-aged open cluster Berkeley 33 , are presented .
The complete R light curve was obtained .
In the present paper , using the five CCD epochs of light minimum ( three of them are calculated from Mazur et al .
( 1993 ) ’ s data and two from our new data ) , the orbital period P was revised to 0.22919704 days .
The complete R light curve was analyzed by using the 2003 version of W-D ( Wilson-Devinney ) program .
It is found that this is a contact system with a mass ratio q = 0.9 and a contact factor f = 4.1 \% .
The high mass ratio ( q = 0.9 ) and the low contact factor ( f = 4.1 \% ) indicate that the system just evolved into the marginal contact stage .