Optical power splitter (OPS) is one of the basic components in photonic integrated circuits and it is widely used in many fields. The OPS with tunable power splitting ratio (PSR) can enhance the flexibility of photonic integrated circuits and simplify the photonic integrated circuit system. We propose an integrated chip scheme Si-based OPS with large tunable range of PSR. The scheme combines Si-based devices such as a symmetric 2×2 multimode interferometer, a waveguide grating, and a slot structure. By varying the wavelength of the input signal and adjusting the voltages applied at both ends of the thermo-optic micro modulator, the wide range adjustable PSR is realized. Experimental results show that the two OPS structure can obtain PSR changes 0.51--36.91 and 0.88--230.46 respectively within the wavelength range of 6.72 nm and 5.56 nm, respectively, and PSR changes of 8.58--29.75 and 5.01--425.43 in the temperature changes by 50 ℃. The OPS has the advantages of small size, light weight, and high flexibility, which can be widely used in optical switch, channel division, power distribution and other communication and signal processing fields.