Based on the analysis of the concept and necessity of prior reliability for dispersion parameters prior distribution

the P value calculating model for given dispersion parameter (variance) was presented

the prior distributions reliability calculating model for onedimensional dispersion parameter was constructed

and the concepts of prior P value and prior reliability were presented. The variation of prior reliability was described

and the reject rule of prior distribution was given. To the analysis of prior reliability for twodimensional dispersion parameter

the independent solution model and integrated solution model for prior P value were carried out respectively. And with the interval divided by 005

02 and 04

the principle and requirement of prior distribution selection was presented. From cases comparison result

it was easy to see that prior reliability can be easy to complete the difference comparison of prior distributions

and compared with traditional method only could describe prior reliability from qualitative view

the P value model not only calculated the numeric of prior reliability

but also could complete the correctness hypothesis test of prior distribution form probability view.