An apparatus for generating multi-phase clock signals with a ring oscillator is provided, including a first stage phase-blender module and a second stage phase-blender module. The first stage phase-blender module further includes a plurality of differential OP phase-blender circuits. Each differential blender circuit has two signal inputs, and an output signal whose phase is an interpolation of the two input signal. The second stage phase blender module includes a plurality of inverter phase-blender circuits. Each inverter phase-blender circuit receives two output signals from the first stage phase-blender module as inputs, and outputs a clock signal with the interpolated phase of the two output signals of the first stage phase-blender module. The present invention also provides a method for generating multi-phase clock signals with a ring oscillator, including the following steps: (1) using a ring oscillator to provide at least two non-full swing signals, (2) using an differential OP phase-blender circuit to blend the phases of two non-full signals from the ring oscillator, and (3) using an inverter phase-blender circuit to generate multi-phase clock signal with interpolated phase.