Spatial bending beams have important applications in optical trapping, fiber sensing, and so on. In these applications, spatial media environment plays an important role. A theoretical method is proposed based on the principle of spatial bending beam excitation. Snell′s law is introduced to invert every geometrical ray of spatial bending beam and describe the refraction of spatial bending beam at air-dielectric interface. Besides, the spatial bending beam is as an example for carrying out simulation based on the finite element method. The refraction mechanism of spatial bending beam at air-dielectric interface may serve as a reference for elucidating the refraction mechanism of arbitrary spatial bending beam motivated by phase inversion.