The invention provides a light emitting diode (LED) illuminating power supply without a transformer. The LED illuminating power supply comprises a main circuit, a stable-voltage constant-current control circuit and an LED power supply interface. In positive half-cycle of alternating current input to the main circuit, the main circuit realizes voltage dividing by means of series connection of a plurality of rectifier diodes and voltage-dividing capacitors which are arranged at intervals to generate direct-current output at a filter energy-storage capacitor; in negative half-cycle of the alternating current input to the main circuit, the main circuit realizes discharge supplementing to the filter energy-storage capacitor by the different voltage-dividing capacitors through corresponding isolating diodes, a common first electronic switch and inductors sequentially to further generate direct-current output. The stable-voltage constant-current control circuit is used for processing sampling voltage signals and sampling current signals and feeding the signals back to the main circuit to guarantee stable working voltage and current of the LEDs. Since the transformer is omitted from the LED illuminating power supply, the power supply is small, light and cheap.