In this paper the design and manufacturing of Iosipesque shear test fixture modification evaluated. This shear test Fixture by applying the shear load in layered of composites specimens can predict the mechanical properties of composite materials in mode II of fracture.In this paper, first, a common traditional Iosipesque shear test fixture according to the standard was manufactured. Then, by applying shear load on polymer-based composites (carbon-epoxy) and wood (a natural composite) specimens, bugs of the traditional fixture were found.Finally by 6 fundamental Modification of the fixture structure, the new design was proposed. It was also found that by applying these reforms, both of concentrating the shear force (in the shear zone) and test accuracy has been increased. Accordingly, after the construction and testing of new fixture on wood and polymer based composite specimens and by applying the standard deviation’s equations, the standard deviation of the modified fixture for wood and polymer based composite has ben reduced 82.7% and 48% respectively, that suggesting the accuracy of the fixture. In addition, fluctuations of the fixtures diagram of the new design also significantly reduced.