Cruciform specimens are commonly used to simulate the complex stress states experienced by engineering components in real-world applications. Biaxial tensile testing of these specimens typically requires specialized biaxial tensile testing machines that are rare and expensive. In contrast, uniaxial tensile testing machines are more widely available and cost-effective but cannot directly perform biaxial tensile tests. To address this limitation, this paper presents the design of a biaxial tensile fixture that enables biaxial tensile testing on uniaxial tensile testing machines. This fixture simplifies the equipment requirements for biaxial tensile testing and can be used for fatigue tests under equal loading conditions. The effectiveness of the fixture was evaluated through strength verification, load error analysis, and experimental testing. Results showed that the specimen failed before the fixture, and the load error was less than 0.4 %, confirming the fixture’s practicality.