This study explores the impacts of directionality on disfluency of sight translation (ST) between English and Chinese. The author adopts four disfluency indicators, namely silent pause (SP), filled pause (FP), repetition (Rt), and repair (Rr) to answer: (1) What are the features of disfluency in ST in two directions? (2) What is the correlation between directionality and disfluency in ST? The results show: (1) The incidence of SP is the highest in both E-C and C-E ST, followed by FP, then Rr, and finally Rt; many student interpreters do the most basic pre-task preparation poorly, leading to a large number of SPs; many SPs coincide with respiration and those over 10 seconds occur only in E-C ST; (2) There are no statistically significant differences between E-C and C-E ST in terms of the four disfluency indicators. In other words, directionality exerts no significant effect on disfluency of student interpreters' ST.