1RXS J201607.0+251645 is identified to be an eclipsing binary .
We present the preliminary observations in V band with the 0.6-m telescope for three years and the extensive observations in V and R band with the 0.8-m telescope for six nights , respectively .
The light curve of the system is EB type .
Five light minimum times were obtained and the orbital period of 0 \fd 388058 ( \pm 0 \fd 00044 ) is determined .
The photometric solution given by the 2003-version Wilson-Devinney program suggests the binary is a semi-detached system with the photometric mass ratio 0.895 ( \pm 0.006 ) , which probably comprises a G5 primary and an oversize K5 secondary .
The less massive component has completely filled its Roche lobe , while the other almost fills its Roche lobe with the filling factor of 93.4 \% .
The system shows a varying O ’ Connell effect in its phase folded diagrams from 2005 to 2007 , and is X-ray luminous with \textrm { log } L _ { X } / L _ { bol } \sim - 3.27 .
Possible mechanisms to account for these two phenomena are discussed .
Finally , we infer the binary may be in thermal oscillation or may evolve into a contact binary .