Abstract: The article is to report some research on the error growth and the atmos-pheric predictability. Some results are obtained by the experiments with a two-level global primitive equations spectral model. The magnitude (RMS) of initial error directly affects the error growth, but its distribution form has little effect on the growth. Small scale error grows rapidly and is transferred to large scale error by interaction between different scale waves, which stimulates the growth of error of whole system. Orographic forcing restrains planetaryscale error (waven-umbers 0-3) and enhances small scale error (wavenumbers 8 or greater) to grow. Hence, orographic effects on the error growth closely depend on the characteristic scale of initial error, and there may be a critical wave number which is between 4 and 7.The error growth is greater in Northen Hemisphere than in Southen Hemisphere when initial errors are the same. In the end we give some discussion about model, initialization scheme, and so on, to improve model prediction.