The structural particles and are often mixed up in the written language, arousing heated debate on whether could be replaced by . However, most of the current studies focus on grammatical or pragmatic differences of these two words, while no studies have been conducted to look into the effect of the mixed use of these two words on information processing and whether there are differences between the effect of two mixed use patterns - for and for . In this study, an eye-tracking experiment with 30 college students was conducted to examine the influence of the mixed use on information processing and whether different patterns have different impacts. The results showed that: 1. the mixed use of and significantly affects the dwell time and fixation count of the whole sentence. In the violation condition, the dwell time was longer and the fixation count was higher; 2. the analysis of the target word showed that there was an interaction between the usage specification (standard or not) and the mixed-use pattern on many eye-tracking indicators, such as first fixation duration, dwell time, regression in times and fixation count, and this influence was mainly caused by for ; (3) the analysis of the remaining sentence after the target word showed different results-there was an interaction between the usage specification (standard or not) and the misuse patterns on fixation count, and the influence is mainly caused by for . On the whole, both for and for caused disruption on readers' reading experience, while for with a low degree of violation had a delayed effect on information processing, which was mainly reflected in the remaining sentence after the target word. The findings of the current research provide evidence from eye-tracking studies for the division of and .