One of researchers’ interests in exploring the mechanism of Simon effect is to determine whether attention plays a critical role in the formation of spacial code. The attention shift account and referential coding account have been proposed to predict modulation effect of attention on Simon effect. However, most studies did not find any change in Simon effect when they manipulate different attention condition, and accordingly, these accounts were not supported by experimental studies. In contrast, some studies did suggest that Simon effect could be modulated by attention. Therefore, there are heated debates on whether attention could modulate Simon effect. In conclusion, we speculate that a possible reason for the contradictory results of previous studies is that the modulation effect of attention on Simon effect is object-based. To test our hypothesis, we used the experimental paradigm of Egly et al. (1994). If the hypothesis holds, we will observe that the object-based instead of space-based attention affects Simon effect. Thirty-four young participants (25 female) were recruited in this experiment. The study consisted of 24 trials full-feedback practice block and four experimental block of 128 trials each. In each trial, a fixation point was presented in the center of the screen, and two rectangular boxes were separately presented either above or below the fixation point, or left or right to the fixation point. After 1000 ms, one end of the rectangular box was flashed as cue for 100 ms. Then a screen with two rectangular boxes was presented for 100 ms. After offset of that screen, the target appeared in one end of rectangular box for 100 ms. Followed by a gray blank screen which was presented for 100 ms. Participants were instructed to respond as quickly and accurately as possible once the target appeared. Finally, a fixation point was presented in the center of the screen with a random duration of 600~800 ms. The E-Prime package was used to present stimuli and record and collect data. The results showed that when the rectangular boxes were vertically arranged, Simon effect had no significant change under the space-based and object-based attention conditions, while when they were horizontally arranged, Simon effect marginally significant increased under the object-based attention condition, but no significant change was found under the space-based attention condition. This confirms that the object-based attention could modulate Simon effect, but the modulation effect significantly depends on the arrangement of rectangular boxes in the paradigm. This study can deepen our understanding of the relationship between attention and Simon effect as well as the formation mechanism of Simon effect.