The measurements of the radial profile of β for two-component plasma were performed on the gas-dynamic trap using the MSE diagnostic. The maximal value of magnetic field perturbation (ΔB/B) was 0.2 allowing to estimate the β as 40%. The profile radius was ≈7 cm, which is only slightly greater than the fast ion gyroradius mapped onto the GDT midplane. The possible mechanisms of a steep plasma pressure profile is under consideration.