The principle of the far field distribution measurement of space laser communication terminals based on the Fourier-transform characteristics of lens is analyzed. The influence of test system with spherical and coma aberrations on the far field distribution of the beam is described and simulated. The simulated results show that the spherical and coma aberrations both reduce the maximum power at the receiving plane and the rotational symmetry of field distribution is only influenced by coma aberrations. The maximum power changes by lower than 0.2% with the root mean squares (RMS) developed. The measurement system is analyzed with Zemax-EE software. The analyzed results demonstrate that the RMS aberrations of the test system are below 0.02λ. The wavefront error of a long focal off-axis Cassegrain optical system is less than 0.0001λ in the working wavelength (800~1700 nm) and good diffraction-limited quality is obtained in full field. The experimental results indicate that the maximum dusky ring dimension error is less than 2.5% compared with the theoretical values. These results prove the feasibility of the far field distribution measurement system.