Abstract: The present invention relates to a modular LED street light including an electrical chamber, a lamp arm, two supporting pipes, an end cap and a plurality of LED light source modules. The LED light source modules are fixed between the two supporting pipes. Each LED light source module includes a circuit board and a radiator. The radiator includes a first plate, two second plates extending from two sides of the first plate and a third plate connected to the two second plates. The radiator has a large area of heat dissipation. When it is required to increase or decrease the number of the LED light source modules for the purpose of increasing or reducing the power of the LED street light, all that is needed is exchanging with lengthened or shortened supporting pipes, thus enabling a power seriation of the street light at very low costs.