||Recently, the kinetics of surface roughening has attracted a lot of attention in statistical physics. For many systems, the roughness is characterized by the roughness exponent and the dynamic exponent. We proposed a model of surface etching which includes the effects of impurity pinning. For 1 dimension, computer simulations showed that when the etching process initiates from the vertices of mesoscopic size (such as in faceted surfaces like quantum dots), the dynamic exponents is 1.331 +- 0.018 for sparsely pinned region, 1.070 +- 0.014 for densley pinned region. These dynamic dynamic exponents are different from the resuils of 1.528 ± 0.016 obtained by starting from a smooth surface, which the KPZ expect at ion is applicable to. We have also investigated the etching process of model with different initial pyramid sizes, and found that the evolution of roughness can be considered as the superposition of 2 processes: evolution of the entire substrate surface, and that of a single pyramid.