The invention provides a light distribution method of a street lighting source and a reflector cup structure thereof. The method and the structure are capable of solving the technical problems that large amount of light from the lighting source can not be projected to the effective parts of the street, and more street lights are needed in per unit length of the street to ensure the continuity of surface brightness. The light distribution method adopts such a mode that the light from the lighting source is reflected by a double-concave double-convex stripy reflective panel which is symmetric to the lighting source, and forms even oblong light spots after being reflected. The reflector cup consists of a long reflective panel, a short reflective panel and a stripy reflector cup arranged at the bottom surface, wherein, the long reflective panel forms a convex arc towards the interior of the reflector cup in the X direction, and forms a concave arc towards the interior of the reflector cup in the X direction; the short reflective panel forms a convex arc towards the interior of the reflector cup in the Y direction, and forms a concave arc towards the interior of the reflector cup in the Z direction. The invention has the advantages of simple structure and low cost, and improves the utilization rate of the lighting source, and is capable of reducing the density of street lights in the unit length of street, thus saving electricity consumption.