The development of field-assisted photocathode was reviewed， and the working principle of field-assisted photocathode was introduced. Three representative cathode structures were summarized systematically， which were InP/InGaAsP/InP， InP/InGaAs and InGaAs/InAsP/InP photocathode. InP/InGaAsP/InP double heterojunction was a research highlight in field-assisted photocathode research， and this structure was mostly used in 1.3 μm field-assisted photocathode； InGaAs heterojunction structure had high sensitivity and fast response time compared with other structures， which was conducive to the application of fringe image converter tube； the photocathode with InGaAs/InAsP/InP structure provided a graded InAsP layer between InP and InGaAs， which was very beneficial to prolong the wavelength threshold. By analyzing the characteristics and applications of different structures， the development direction and difficulties of field-assisted photocathodes were discussed.