The coherent state orthogonalization expansion method is used to analyze and investigate the factors influencing the three-qubit entanglement degree. In addition, the three-qubit entanglement in the interaction process with the vacuum state as the initial state of the light field is investigated by numerical calculation combined with analytical solution. The relationship between the entanglement degree of three identical qubits and the light field frequency as well as the influence of light-field-qubit coupling strength on the three-qubit entanglement degree is analyzed. The research results show that the evolutions of the three-qubit intrinsic energy and the three-qubit co-occurrence entanglement degree with light field frequency and time g0t are related to the coupling strength, while the evolutions with time gt have nothing to do with the coupling strength.