Abstarct: The Schrodinger equation of a Cavity QED-atom system has been solved by considering the ultra strong coupling and Casimir effects in Rabi model. Derived solutions can be applied to find the entanglement of the system through concurrence and trace diatance. Cazimir effect and ultra strong coupling have reverse influence on the system.The ultra strong coupling stabilize the cavity-atom system. As the situation is a pure 2n system thus one can find both trace-distance and concurrence through the reduced density matrix of the qubit. In such these systems trace-distance approximately behave like the concurrence.