Traditional analytical theory design scheme faces problems, such as high computational complexity, limited analytical solution, and high time-consumption. To cambat these issues, based on the design of traditional optical devices, a scheme for designing an optical power splitter with adjustable split ratio according to the reverse design method is proposed. In a compact region of 1.92 μm×1.92 μm, Ge₂Sb₂Se₄Te₁(GSST) is introduced to change the refractive index distribution of the device. The direct binary search algorithm is utilized to search the optimal state distribution of GSST in crystalline and amorphous states. A T-shaped optical power splitter with adjustable split ratio is designed and implemented for the same device structure. The initial structure, split ratio, phase change material region state distribution, manufacturing tolerance, and light field distribution of the device are simulated and analyzed. The results show the minimum relative errors of the designed optical power splitters with three splitting ratios of 1∶1, 1.5∶1 and 2∶1 between wavelengths 1530 nm and 1560 nm are 0.004%, 0.14% and 0.22%, respectively. The maximum fluctuations of the transmission curve in the manufacturing tolerance range are 0.95 dB, 1.21 dB and 1.18 dB, respectively. The splitter has a compact structure and great potential for applications in optical communication and information processing.