It will be a future trend to apply quantum photonic technology to communication technology and information processing. One of major developing directions of quantum photonic technology is the miniaturization and on-chip integration. Resembling the diodes in integrated electric circuitry, optical unidirectional transmitter devices (UTDs) plays an important role in quantum information processing and also represents the main component of integrated optical devices. Thus, the design of UTDs has become one of the research hotspots. With photonic bandgap and localization characteristics, as well as easy micro-nano scaled integration, photonic crystals (PCs) are often preferred when it comes to develop micro-nano integrated optical devices. At present, the common methods of achieving UTD with photonic crystals include directional bandgap mismatch, asymmetrical coupling by a micro-cavity, odd-even mode conversion, photonic crystals with grating and photonic crystal heterostructure total reflection etc.. However, these optical unidirectional transmitters gained through the above methods generally have a low forward transmission, narrow working band, complex structure and so on. The paper put forward to a novel method of UTD based on photonic crystal and designed a UTD of funnel-shaped waveguide. The design of the device is divided into two parts: funnel waveguide design and point defect design optimization. The band structure of TM polarized photonic crystals is calculated by R-soft. A triangular lattice circular air hole photonic crystal with complete photonic band gap was used as the initial structure and line defects were introduced to form a funnel-shaped waveguide structure (FSWS). FSWS consists of a first waveguide W1, a second waveguide W2 and a funnel cavity. The funnel cavity is shaped like a funnel and located at the coupling between W1 and W2. Due to the unique characteristics of the waveguide, the light wave transmission will be localized in the waveguide, which is conducive to improving the forward transmission. The influence of width variation of W2 with forward and backward incident light was analyzed by the finite difference time domain (FDTD) method, and W2 was selected as the waveguide formed by removing 11 rows of air holes. FSWS achieves the initial asymmetric transmission, while the backward transmission remains high. Further studies were conducted to introduce four types of point defects to suppress the backward transmittance. Point defects are referred as moving one or two air holes. The research also use FDTD to calculate four kinds of point defect backward transmittance spectra and optimize the position of point defects. Finally, it was found that when the optimal point defect mode was type I and d = 5a, the forward transmission (Tf) and transmission contrast (C) at 1550 nm were 0.716 and 0.929, respectively. Working bandwidth (B) can be up to 111 nm (1501 nm - 1612 nm). By mode analysis, it is found that the point defect introduces mode mismatch between W1 and W2, by converting the fundamental mode in W2 to high order modes. Thus, the back-propagating light waves in W2 cannot effectively couple into W1, resulting in complete blockage of backward propagation. In addition, the structure is made of silicon base air hole photonic crystal. 2D air-hole PC slab is mature and even compatible with conventional complementary metal oxide semiconductor (CMOS) processing. The designed UTD is easy to implement, has the advantages of simplicity and high unidirectional transmission characteristics. Therefore, it can provide a new solution for UTDs with higher requirements of integrated optical path at present.