  We have analyzed the motion of an infinitesimal mass in the restricted four
body problem with solar wind drag. It is assumed that forces which govern the
motion are mutual gravitational attractions of the primaries, radiation
pressure force and solar wind drag. We have derived the equations of motion and
find the Jacobi integral, zero velocity surfaces and particular solutions of
the system. It is found that three collinear points are real when radiation
factor $0<\beta<0.1$ whereas only one real point obtained when
$0.125<\beta<0.2$. Again, stability property of the system is examined with the
help of Poincar\'{e} surface of section (PSS) and Lyapunov characteristic
exponents (LCEs). It is found that in presence of drag forces LCE is negative
for a specific initial condition, hence the corresponding trajectory is regular
whereas regular islands in the PSS are expanded.
