Using linear programming method in control allocation for attitude control subsystem of spacecraft with redundant thrusters is studied in this paper. The simplex algorithm is utilized as a solver and the Direction Preserving and Bodson’ s Reduced size Direction preserving approaches are used as optimal approaches to deal with non admissible solutions. Also, proper functioning of these approaches against thrusters fault phenomenon is evaluated. The results show that the Direction Preserving approache has less computational time and less fuel consuming. However, the Bodson’ s Reduced size Direction preserving approache has more computational time and more fuel consuming but less tri-axis tracking error. It should be noted that the PD controller has been used as a spacecraft control rule, and simulations have been made for the number and configuration of the specific thrusters.