The introduced design is a 1 × 8 optical power splitter using MMI structure and taper output branches in GaN semiconductors. The design has been conducted theoretically using 3D FD-OptiBPM to improve the power distribution. The modelling structure used 300 nm AlN and 200 nm AlGaN as the buffer layer on Sapphire respectively. The numerical experiment is carried out at an optical telecommunication wavelength at λ = 1.55 μm. The refractive indices of the layers used are n
= 2.279 ± 0.001 and n
= 2.316 ± 0.001. The result showed that the optimum width and thickness of input and output rib waveguides are 4 μm and support only single mode propagation. The MMI-based optical power splitter with a length of 2010 μm and a width of 85 μm is the best result. In this proposed design, the output power splitted in almost uniform into eight output branches. It is also shown that the total relative power at the output ports is 0.96 with an excess loss of 0.28 dB and power imbalance of 0.13 dB.