The invention discloses a side light-emitting optical fiber with openings at a side end and a manufacturing method thereof as well as a backlight module. The side light-emitting optical fiber with opening at the side end comprises: an optical fiber body, a baffle and an opening groove, wherein a plurality of groups of main light leakage holes and a plurality of groups of auxiliary light leakage holes, which are distributed linearly, are formed in a core diameter; the main light leakage holes and the auxiliary light leakage holes are distributed in a staggered manner; the auxiliary light leakage holes are used for adjusting the illumination intensity of the main light leakage holes and tail light so as to enable the illumination intensity of whole light leakage on the optical fiber body to be uniform; the baffle is fixed at the tail end of the optical fiber body and an included angle is formed between the baffle and the core diameter of the optical fiber body; the opening groove sleeves an outer side of the optical fiber body; an opening side of the opening groove corresponds to the main light leakage holes and the auxiliary light leakage holes; an edge side of the opening groove is further connected with the baffle. By adopting the side light-emitting optical fiber with opening at the side end, the brightness of a light source can be adjusted, and the side light-emitting optical fiber is high in color saturation degree, simple in structure and convenient to use. Meanwhile, when a large-power laser device is used, a heat dissipation problem can be solved very well under the condition that the size of the backlight module is not increased.