The stability and reliability of inversion can be modified and improved by controlling the quality of inversion intermediate results. The reflectivity modeling method and conjugate gradient inversion method are used in this paper. In the process of inversion

the negative gradient is lined up according to the horizontal slowness to form the negative gradient panel in a slowness-depth domain. In the negative gradient panel the gradient represents the contribution provided by data with different incident angles (i.e. different horizontal slowness or ray parameter). Thus

the negative gradient panel has the similar meaning as the common imaging point gather in migration and can be used for tool controlling process of inversion. The roles of quality control that the negative gradient imposed on the process of inversion are discussed from the following aspects: the rationality assessment of the inversion initial value; the correctness evaluation of parameter selection when using three inversion strategies

especifically

the correctness evaluation of the frequency-band selection in frequency-division inversion

the correctness evaluation of the layer segment selection in layer-division inversion

and the correctness evaluation of the slowness components selection in slowness-division inversion. The test using model indicates that the quality control for inversion intermediate results based on negative gradient panel is feasible.