Abstract: In this paper, A new low-loss wide-angle Y-Junction with graded-index optical waveguides, which can change the optical propagation direction, is introduced. An application of the Y-junction structure to 1×4 optical splitter and Mach-Zehnder modulator is analyzed. The two kinds of device performance are examined numerically by the finite difference beam propagation method (FDBPM). The simulated results show that the 1×4 optical splitter has very low loss of 0.32 dB but its optical waveguide length can largely be shortened, and that the M-Z modulator can reach a counteraction of the coherence light when the branching angle is 14.3°. Comparing with common devices, optical splitter and M-Z modulator with low-loss wide-angle Y-Junction have both low loss and small dimension.