Light-control splitting ratio tunable Y-type Terahertz waves to beam splitter based on two-dimensional photonic crystal is proposed. In this scenario， the feature that coupling with line defects and the point defects of nonlinear polymer materials which have the third-order nonlinear Kerr effect is utilized. The performance of Terahertz waves splitter with tunable splitting ratio is studied by Plane Wave Method （PWM） and Finite-Difference Time-Domain （FDTD）.The research results show that the Y-type Terahertz wave splitter with tunable splitting ratio of two output ports by changing the light intensity of the control light can be realized.This beam splitter which the transmittance reaches over 98% can achieve Terahertz waves splitting with a specific wavelength. At the same time， the additional loss is less than 0.087dB and the response time reaches the order for ps.The splitter with tunable splitting ratio will have broad application prospects in future Terahertz wave communication.