Based on analysis of light intensity distribution over exit face, effects of direction angle of laser beam on exit optical field distribution were investigated during transmission process through optical fiber. A new influencing factor was proposed, which was a complement to the two proverbial factors-numerical aperture and core diameter of the optical fiber. Beams of laser diode were resolved into a large amount of ray during transmission process. On the condition of a constant entrance optical field distribution, influences of single beam and multi-beam direction angle and optical fiber length were analyzed by ray tracing method. Results indicate that, in optical fiber, deviation of a single beam direction angle can lead to extremum position excursion on the exit face, while with more beams, deviation of direction angle can bring about an obvious ring form light intensity distribution. It can be concluded that direction angle of a beam is an important factor which influences the light intensity distribution and extremum position over the exit face, and the length of optical fiber also takes effect.