A triangle road sign having a bottom rack, a left frame bar and a right frame bar respectively pivoted to two distal ends of the bottom rack and detachably coupled to each other to form a triangle rack with the bottom rack, a device for securing the triangle rack to the inside of a car, indicator lights respectively installed in the bottom rack, the left frame bar and the right frame bar and controlled to flash by a control switch at the bottom rack, a solar collector installed in the bottom rack to collect solar energy and to convert collected solar energy into electricity for the signal lights at the bottom rack, the left frame bar and the right frame bar, a battery box installed in the bottom rack and controlled by the control switch to provide the necessary working voltage to the signal lights, an alternating current adapter controlled by the control switch to convert alternating current power supply to direct current power supply for the signal lights.