Lithium niobate crystal has many advantages such as large electro-optical, piezoelectric and non-linear optical coefficients, wide optical transparency range, compatibility with speed matching, phase matching and dispersion engineering, long-term stability and low-cost preparation of optical-grade wafers. As an important platform for constructing optoelectronic devices such as electro-optic modulators, optical frequency combs and optical waveguides, lithium niobate holds grant promise in the fields of light generation, light transmission and light modulation in the field of information and communication. Lithium niobate is also well known as the “silicon of photonics” and has huge integration potential in both academia and industry. However, due to the insulator and weak optical absorption properties of lithium niobate, integrated application fields based on lithium niobate platforms also face the problems of low photo-to-electric conversion efficiency and thus arouse difficult in photodetection. Light demodulation and light extraction in all-optical communications require high-performance detectors, therefore, the development of photodetectors based on lithium niobate has great scientific significance and application value. Starting from the basic structural characteristics of lithium niobate, this article introduces in detail the excellent physical properties and photo-to-electric conversion mechanism of lithium niobate, reviews some recent research results of domestic and foreign scholars, and focuses on the optical waveguide integrated photodetectors and the heterogeneous type photodetectors based on lithium niobate crystals, the advantages and development potential of different routes are discussed and compared, and prospects for this field are proposed.