Visual working memory (VWM) performance can benefit from the Gestalt principles of similarity and proximity in the change-detection task. A fundamental issue in this field is how similarity together with proximity influences the VWM representations. One view postulated that the positive effect of similarity on VWM performance was constrained by proximity, such that similarity was effective only when the similar items were near each other in an ordered spatial configuration of memorized items. The other assumed that such effect of similarity could occur regardless of proximity of similar items in a random spatial configuration of memorized items. However, the order of spatial configuration, as a basic organization rule, was not controlled in previous studies of the effect of similarity and proximity in VWM. Such similarity effect might be influenced by the order of spatial configuration for memorized items. Therefore, a crucial test of such fundamental issue is how proximity and the order of spatial configuration influence the similarity effect. We examined how proximity influenced the similarity effect in VWM with the orderliness of spatial configuration of memorized items using a change detection task. Proximity of similar items was manipulated by the distance and the inserted other item between similar items. The proximal condition was the decreased distance between similar items without inserting other item. The non-proximity conditions were the decreased distance between similar items with inserting other item, as well as the increased distance between similar items with or without inserting other item. Furthermore, the present study employed ordered and random spatial configurations of memorized items in experiments 1 and 2, respectively. In Experiment 1, it investigated whether proximity influenced the similarity effect when spatial configuration was in order. Participants were asked to remember 6 colored circles that were located on an imaginary circle (i.e., ordered spatial configuration). In Experiment 2, it aimed to investigate whether proximity influenced the similarity effect when spatial configuration was random. Participants were required to remember 6 colored circles that were presented at random locations around the center of the screen (i.e., random spatial configuration). The hypotheses were that the increased distance and the inserted other item between similar items could impair the similarity effect when spatial configuration of memorized items was in order, and that such proximity could not influence the similarity effect when spatial configuration was random, given the salient cue of similarity in the random spatial configuration. The results showed that the accuracies of similar items were higher than those of dissimilar items in both ordered and random spatial configurations, regardless of proximity of similar items. Furthermore, inserting other item between similar items attenuated the similarity effect when the similar items were far from each other for the ordered spatial configuration, but not for the random spatial configuration. These results suggested that similarity could facilitate VWM performance regardless of the order of spatial configuration for memorized items. Such similarity effect on VWM performance was constrained by proximity only when the spatial configuration of memorized items was in order.