Abstract: In this paper, the spectral lines of hydrogen and ionized calcium, as well as their center-to-limb variations, observed at Kitt Peak National Solar Observatory, are used to diagnose the VAL-C', quiet Sun atmospheric model. The PANDORAcomputer program is used to perform the detailed non-LTEmodel calculations, especially for hydrogen and calcium. The main discrepancies between the computed spectral lines and the observed data are: (1) The residual intensity in Hβ andλ8498 line centers is evidently higher, while that in CaII Hand Klines are relatively lower than the observed values; (2) The center-to-limb enhancement coefficient of the residual intensities of Hβ, and all the CaIIlines (resonance and infrared lines) near Δλ = 0.5Å is a little larger than indicated by the observation. However, all other spectral features observed can be reproduced fairly well. Finally, the possible causes which can make the computed values deviate from the observed ones is discussed, and a comment on revising the VAL-C' model is given.