The effects of B content on the durability of GH4738 nickel based superalloy were studied by SEM, TEM and EPMA. The results show that B content can significantly improve the content and distribution of M₂₃C₆ carbides at grain boundaries, improve the precipitation and dispersion uniformity of M₂₃C₆ at grain boundaries. B element is mainly concentrated in the carbide in the alloy, and may participate in the carbide precipitation as a carbide forming element. The content of B has no effect on the precipitation of γ "strengthened phase. With the increase of B content, the durability of the alloy is improved, the durability life increases by 8~12 times, and the durability plasticity increases by 2~4 times. The permanent fracture mode changes from brittle intergranular fracture to mixed fracture. The effect of B content on the tensile properties of the alloy is small, and the effect decreases slightly due to the slight increase of grain size.