coherent-state method [@chen; @mao15], and a generalized RWA (GRWA) [@irish; @zhang]. Recently there have been interesting applications of the Dicke model [@dicke] with three qubits in the quantum information technology, such as the application of the Greenberger-Horne-Zeilinger states [GHZ]{}. And the circuit QED has entered the deep-strong-coupling regime  [@Yoshihara], so it is experimentally possible to realize the three-qubit Dicke model in circuit QED in the ultra-strong- and deep-strong-coupling regime [@sonalo]. We will present an analytical solution to a three-qubit Dicke model. However, explicit analytic solutions to the three- and more-qubit Dicke model have not been extensively studied. Despite the fact that the exact solution to the three-qubit Dicke model has been given by a Bargmann space technique [Braak1]{} where a numerical search for the zeros of very complicated transcendental functions is needed, an efficient, easy-to-implement theoretical treatment remains elusive. In this paper, we extend the previous GRWA in the one-qubit Rabi model by Irish [@irish] to the three-qubit Dicke model. Including the CRW interactions, we successfully derive a solvable Hamiltonian with the same form as the ordinary RWA term. Therefore all eigenvalues and eigenstates can be approximately solved and can be implemented with great ease by experimentalists.

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