On the basis of the Mach-Zehnder optical interference model, a digital holographic interferometric experimental system was set up, and a new diffusion cell especially for measuring the binary gas diffusion coefficient was designed and constructed. With the theory for measuring the binary gas diffusion coefficient and the interference fringe processing method introduced before, the binary gas diffusion coefficient can be obtained. In comparison with the reference data of O(2) in air, the experiment accuracy of the system was verified. The diffusion coefficients of H(2), He, NH(3), CH(4), O(2), and CO(2) in air at T = (278.15 to 343.15) K under normal atmospheric pressure were measured and compared with results of a correlation. The comparison showed that the results are reasonable.