Abstract: There are three manners of spiral cases embedment in concrete in TGP, i.e., spirals are embedded with keeping constant internal pressure, embedded with cushion layers and embedded directly. The turbine units on the left bank, in which the spiral case was embedded with constant internal pressure, have operated safely for some years.? Applying the spiral case embedded directly in large scale turbine was the first time in domestic project. In order to compare and analyze the structure cracks and displacements under different embedded manners, and furthermore, to provide a reference for cushion layers method and embedded directly method, crack analysis on the spiral case flow passage and outer reinforced concrete structure was carried out. The distribution of cracks, stresses of steel liner and rising displacements of the structure were studied. The computed results showed that the concrete cracks range and rising displacements of the structure are the largest in direct embedment? manner, that those are the least in embedment manner with keeping constant internal pressure, and that there is a little difference result between cushion layers manner and keeping constant internal pressure manner, therefore, two manners can be adopted successfully in TGP turbine units. The direct embedment manner can also make the units operation safety when the effectively strengthening structure measure is adopted.