Abstract: This research was designed to explore the role of sentence boundaries and buffer time in priming the integration of background information during reading process. Three experiments were administered. Ss were 198 university students The on-line window display technique was used and the Ss were asked to read 14 discourses which included the consistent version and inconsistent version. The time of reading the target sentences and responding to the probe words in different conditions were analyzed. In Experiment 1,the research made by Guzman & Klin in 2000 was replicated under the condition with Chinese materials. And it was further explored whether only the sentence completion could prime the on-line information integration. The results showed that the difference of the times both in reading the target line and in responding the probe approached significant level between the consistent condition and inconsistent condition under the condition of only sentence completion. It was indicated that background information integration was primed immediately during the course of reading the target line.In Experiment 2, it was examined whether the results which indicated the buffer time could prime the information integration on line in the experiment by Guzman & Klin in 2000 mixed the effect of sentence completion. The results showed that adding the conjunction to the end of target sentence could become the cue of sentence completion and immediately prime the integration. It was indicated that the conclusion got by Guzman & Klin was doubtful. In Experiment 3, it was further explored whether only the buffer time was sufficient to prime the background information integration on line without the sentence completion cue. The result showed that only the buffer time could not prime the on-line information integration. It can be concluded according to this research that the factor of sentence completion can prime the on-line background information integration during reading course and the buffer time can not do so