Abstract: Fiber reinforced polymer (FRP) bars are increasingly used in civil engineering. In the application, FRP bars are commonly used as tensile bars, and therefore their tensile strength is an important indicator of mechanical properties. Due to the low shear strength and local bearing strength, it’s a big challenge to anchor FRP bars in testing its tensile strength. However, the shear strength of FRP bars can be easily tested. Therefore, evaluating the tensile strength of FRP bars via shear strength is a way to reduce the difficulties associated with the testing of FRP tensile strength. Moreover, FRP bars are commonly subjected to the combined action of shear and bending, and the accurate evaluation of their shear contribution should consider the ratio of shear to tensile strength. Therefore, it’s of great significance to establish the relationship between the transverse shear strength and tensile strength of FRP bars. Unfortunately, existing studies on the relationship between shear and tensile strength of FRP bars are scarce. In view of this, this paper designed a series of CFRP bar, GFRP bar and BFRP bar samples for shear and tensile tests. Based on the test results, the size effect of the shear and tensile strength of FRP bars and the shear- tensile strength relationship were investigated. Test results showed that, the shear and tensile strength of FRP bars reduced with the increase of bar diameter, and the shear strength was about 18%~20% of the tensile strength. Utilizing the test data of the present study and test data from the literature, the machine learning prediction model for shear and tensile strength of FRP bars is established. The trend of prediction results is in the good agreement with the trend of experimental results.