The ability of language understanding plays an important role in today's highly technical society, the language comprehension ability of hearing-impaired students is so poor that people should pay attention to the study of language comprehension of them, in order to improve their social adaptability. Discourse comprehension is an important part of language comprehension, and from the perspective of improving social adaptability, discourse comprehension is a topic with more ecological validity. Deaf students receive information in the form of oral, sign and written language. Which way is the most efficient? To address the above question, we performed two experiments in this study, in which within-subject design were used. Participants in this study were students from the seventh, eighth, and ninth grades of the school for the deaf. They were all prelingual deafness students and had hearing loss of more than 90 dB. The study presented narrative and descriptive texts through videoes in three input modes of oral language, sign language and written language. Participants were required to complete micro and macro test questions after watching the video. The researchers examined the impact of information input modes, text types, and test types on deaf students' discourse comprehension. The results of the F-test for the data from Experiment 1 showed that the input mode had a significant main effect, the main effect of the text type was not significant, and the interaction between them was significant. That was to say, text type was a moderator. The main effect analysis of input mode showed that the participants had highest score and fastest speed when the texts were shown in written language. The score and speed were in middle when texts were presented in sign language. The score was lowest and the speed was slowest when texts were shown in oral language. The F-test for the data from Experiment 2 showed that test type regulated the interaction between input mode and text type. Deaf students had the highest comprehension efficiency of the text presented in written language, but the lowest of spoken language. For the narrative text , written language is the most efficient way for them to receive discourse information. They got the highest micro understanding score for the descriptive texts under oral language condition, while got the highest macro understanding score under sign language condition. To help the deaf students improve the efficiency of descriptive discourse comprehension, the combination of speaking and sign language is a good choice. Spoken language helps students to understand and remember the details, while sign language helps students to grasp the overall information of the discourse. When evaluating deaf students' discourse comprehension, input mode is the main influencing factor. At the same time, the influence of text type and test type should be considered. The evaluation index should include score and speed.