Abstract: Aiming at the problem that the uniaxial tensile testing machine cannot achieve the biaxial tensile test, a biaxial tensile fixture capable of accurately converting the uniaxial tensile motion into the biaxial tensile motion is designed. First, the basic principle and motion mechanism of the biaxial stretching jig is introduced; then, a biaxial tensile test is performed with a bacterial cellulose hydrogel cross tensile sample, and the comparison of the horizontal and vertical tensile displacement is performed to complete verification of the accuracy and reliability of biaxial stretching movements. The results show that the linear regression relationship between the vertical displacement Y and the horizontal displacement X is Y=0.999 8X+0.002, the determinants of coefficient R²=1. The standard tolerances between the horizontal displacement and the vertical displacement within 0 to 10 seconds are almost in the level of one in a thousand. The test results suggest that the biaxial tensile fixture could transform a uniaxial tensile motion into a biaxial one. It can successfully realize the biaxial cruciform tensile test based on the uniaxial tensile testing machine.