A lighting system for plant cultivation which is established on a planting system planted with a plurality of plants is provided. The lighting system includes an illumination module and a ring transformer module. The illumination module includes a plurality of light emitting units and a power connection port. Each of the light emitting units includes a plurality of light emitting diodes (LEDs) that emit light towards the plants when powered. The ring transformer module includes a ring core, a primary coil winding around the ring core, and a secondary coil winding around the ring core. A non-harmonic power is provided by the one single ring transformer module for powering the light emitting units, thereby solving issues of power consumption and heat dissipation caused by conventionally disposing an electronic rectifier in every of the light emitting units.
