The unidirectional transmission of light waves based on photonic crystal heterostructures is of great significance in all-optical networks and optical signal processing. Based on the total reflection principle, two kinds of triangular lattice photonic crystal waveguide heterostructures are designed by using silica and germanium materials. The finite difference time domain method is used to analyze the unidirectional transmission performance in a broad bandwidth. The structure is further optimized by changing the waveguide width at the forward exiting end. The results show that in the heterostructure one, the forward transmittance of TE mode wave is higher than 0.8 in the wavelength range from 1458 nm to 1517 nm, and the transmission contrast is higher than 0.9 with unidirectional transmission. In heterostructure two, the forward transmittance of TM mode is higher than 0.8 in the wavelength range from 1498 nm to 1689 nm, and the transmission contrast is close to 1 with unidirectional transmission.