Perceptual span refers to the area of effective vision from which useful information can be obtained during a fixation in reading (McConkie and Rayner, 1975 ; Rayner and Pollatsek, 1989;D. Shen et al.,2008). Research has demonstrated that skilled adult readers of Chinese obtain useful information from an asymmetric region extending roughly 1 character spaces to the left of fixation to about 2–3 character spaces to the right of fixation. To determine the size of the perceptual span, the classic gaze-contingent moving-window technique was developed (McConkie and Rayner, 1975 ). In this technique, the text outside a pre-defined window around the point of fixation is masked by Xs or scrambled letters. Thus, wherever the reader looks, the text is visible within the window, but outside the window the text is disrupted in some way. By varying the masking material, the researcher have found the perceptual span is different in English and other alphabetic writing systems In the present study gaze-contingent moving-window technique was used to explore the effect of masking material on perceptual span of Chinese reading. 26 college students participated. Their eye movements were recorded with a SR Research EyeLink eye tracker. 130 sentences were presented in seven viewing conditions (R1、R2、R3、R4、L1R4、L2R4 and whole line) to examine the perceptual span of college students in different masking conditions. The results showed: (1) Compared with symbol masking condition, the reading efficiency in character masking conditon was lower, average fixation time was longer and saccade amplitude was smaller. (2) The participants could obtain useful information from an asymmetric region extending roughly 1 character space to the left of fixation to about 2–3 character spaces to the right of fixation in the symbol masking condition, and the perceptual span extended 1 character space to the left of fixation to about 3–4 character spaces to the right of fixation in the character masking condition. In summary, the perceptual span is larger but the reading efficiency is lower in the character masking condition than those of symbol masking. Perhaps character is more approriate to be used as the masking material to study the perceptual span in Chinese reading.