The Compton profiles of nitric oxide and acetylene molecules have been determined at an incident photon energy of 20 keV. Compton profile measurements are carried out with the beamline BL15U1 at the Shanghai Synchrotron Radiation Facility (SSRF). A dedicated gas cell is used, in which diffuse scattering is effectively suppressed. By considering that the statistical accuracy of 0.2% at pz ≈ 0 is achieved, the Compton profiles of NO and C2H2 determined in this paper can serve as the experimental benchmark data. Furthermore, the density functional theory (DFT) and HF calculation for different basis sets are used to calculate the Compton profiles of nitric oxide and acetylene. It is found that the DFT calculations with the diffuse basis sets are closer to the experimental results, indicating that the electronic density distribution of nitric oxide is more diffuse. For acetylene, the HF calculation is of better agreement with the experimental result. To better understand Compton profiles, we have compared them with distributions of electron density by theoretical calculation. There are clear correspondences between them: diffuse distribution is related to the localized profile and complex structure in electron density distribution, which also shows a subtle structure in profile. The present Compton profiles of nitric oxide and acetylene molecules achieved by synchrotron radiation are the most accurate up to now, as far as we know.