As an important accelerator neutron source, neutron generator is widely used in neutron radiography, irradiation damage research, irradiation breeding, activation analysis, cancer treatment, oil exploration, nuclear data measurement and so on (Long et al. in A novel method to survey parameters of an ION beam and its interaction with a target (166–171, 2017) [1]; Liu et al. in Surface characteristics of titanium deuteride film implanted with deuterium ion beam (62–67, 2014) [2]; Reijonen in Neutron generators developed at LBNL for homeland security and imaging applications (272–276, 2007) [3]). The target is the key component of the neutron generator. The target is composed of two parts: the target film and the substrate. The substrate is the carrier of the target film material. The target film is the interface where the deuterium–tritium reaction produces neutrons. Therefore, the characteristics of the target are the key factors affecting the neutron yield and service life of the neutron generator. Titanium (Ti) is the most commonly used target film preparation material. The hydrogen absorption density of titanium is as high as 9.2 × 1022 hydrogen atoms/cm3, which can adsorb a large amount of tritium and provide sufficient raw materials for neutron production. The dissociation pressure of titanium tritide at room temperature is low, only 10−5 Pa, which makes it one of the ideal materials for preparing solid tritium targets (Batistoni et al. in Neutronics and nuclear data issues in ITER and their validation (834–841, 2008) [4]). Neutron yield is an important index of neutron generator. In the study of Fang Hua et al. (Xi et al. in The influence of target film properties on the yield of neutron tube (28–30, 2013) [5]), it was found that the purity of target film material, coating process and target film thickness are the key factors affecting neutron yield. On this basis, this paper briefly introduces the basic structure of tritium target for sealed neutron generator, the principle of neutron generation and the basic requirements of tritium target preparation, including high thermal stability, strong helium fixation ability, radiation resistance, sputtering resistance and oxidation resistance. On this basis, the research progress of substrate, target film material, protective layer and target making process of metal tritium target in the past two decades is reviewed. The research direction of tritium target for neutron generator in the future is put forward, which mainly involves the research and development of new target film material, the improvement of target making process and the optimization of target cooling system.