In a two-dimensional plane, the characteristics of a light field near the focus of a 1D convergent GB are analyzed using a 1D diffraction integral formula. As the normalized inclination factor that is expressed by the square root of the cosine of the observation side inclination angle is engaged, the characteristics of the focal-plane light field of the 1D nonparaxial convergent GB that is expressed by a new diffraction integral formula conform to the law of conservation of radiation energy in traveling wave field, the characteristics of a light field near the focal line of the 1D nonparaxial convergent GB are reasonable. Then, the propagation characteristics of the GB are extended from the paraxial field to the nonparaxial field using the reasonable observation side inclination factor. Furthermore, the rationality of the observation side inclination factor expressed by the square root of the cosine of the observation side inclination angle is verified.