On the basis of the number fluctuation model of n-type metal oxide semiconductor field effect transistor （nMOSFET），non-Gaussianity of noise in nMOSFET was studied by the quadratic sum of the bicoherence，which belongs to higher order statistics. Comparing nMOSFETs test noise with Monte Carlo simulative noise，we proved that there is non-Gaussianity in nMOSFTs noise, that the noises non-Gaussian degree in small size devices is stronger than that in large size devices, and that the non-Gaussian degree of nMOSFTs noise in strong inversion and linear regime increase with the drain-source voltage. The physical mechanism of nMOSFET noise is discussed from Monte Carlo simulation and the central limit theorem.