Background: One of factor that increases the flexural strenght of fiber reinforced acrylic resin is a fiberglass position . Fiberglass is one of type that can be used in dentistry. The aim of this was to determine the influence of position of fiberglass to the flexural strenght of fiber reinforced acrylic resin. Method: This study was in vitro laboratory experimental. Samples was 16 plate spesimens (65x10x2.5mm). The study group was divided into 4 group : 3 groups of fiber reinforced acrylic resin were given fiberglass at the upper, middle, and bottom side and 1 control group of resin acrylic without fiberglass. All of groups would be in the flexural strenght test with a three-point bending test using a universal testing machine. Result: Based on One Way ANOVA test showed that there were significant value 0.000 (p<0.05), it concluded that there were significant influence between all the groups. Based on the LSD Post Hoc test showed that there were significant value between all of groups with fiberglass reinforced and control group without fiberglass reinforced. Comparisson between the group that given fiberglass in a upper and middle side with the group that given in bottom side showed value of significant difference (p < 0.05). Conclusion: The result of study was concluded that there was an influence on the position of fiberglass to flexural strenght of fiber reinforced acrylic resin