In this study, hydrogen production processes by plasma gasification of three different algae were proposed. The processes were comprehensively analyzed and evaluated in terms of thermodynamic efficiency and economic benefits. The results showed that the hydrogen production processes of Enteromorpha by plasma gasification had the best performance and the exergy efficiency of the plasma gasification was as high as 74.46%. The total efficiency of the hydrogen production process of Enteromorpha by plasma gasification was 33.92%, which was 3.87% and 3.63% higher than that of the Cyanobacteria and Sargassum process, respectively. The high exergy loss of the acid gas removal and plasma gasification unit accounted for 80.14%–83.53% of the total exergy loss. In addition, the Enteromorpha process also had better economic benefits compared to the other two processes, which was greatly affected by feedstock and electricity prices.