Abstract: The changes of pore volume in dolomitization is essential to the reservoir properties. Recently, there are three kind of views in recongnizing the change: 1.There is an increase of pore volume during dolomitization; 2.There is a decrease of pore volume during dolomitization; 3.There is no volume change during dolomitization. The author suggests that dolomitization is nearly a volume for volume replacement. There is little effect on pore volume in simple dolomitization. The author presents 2 models of the formation of "Sucrosic" dolostoen which preserved good reservoir properties. (1) Replacement-soution model, and (2) Replacement-conversion model. The formetion of "Sucrosic" Dolostone is not an inevitable result of dolomitization but a product of specific dolomitization environment and certain textural condition.