Abstract: An LED includes a cooling block, an LED chip, two insulating layers, two electrically conductive layers and two gold wires. According to the invention, two open trenches are arranged by opening on the cooling block; the LED chip is fixed on a surface of the cooling block; the insulating layers are plated on inner walls of the trenches; the electrically conductive layers are plated on the insulating layers and are insulated from the cooling block; the gold wires are electrically conducted to the electrically conductive layers and the LED chip; since the insulating layers are only plated on parts, where the cooling block contacts the electrically conductive layers, the other parts of the cooling block are exposed, such that the cooling area is increased and the cooling performance is promoted; in addition, the invention is further to provide a cooling block assembly constituted by these cooling blocks.