We analyzed the relationship between several basic parameters describing supermassive black holes such as jet power, black hole spin, accretion disk magnetic field, black hole mass, etc. We found that there is a general correlation between these parameters, such as jet power is significantly positively correlated with black hole spin, while black hole mass is significantly negatively correlated with black hole spin. To apprehend these relationships, we consider the Blandford-Znajek model to be superior to the Blandford-Payne model. It is also found that the intrinsic gamma luminosity of the FSRQs has a positive correlation with the accretion disk magnetic field, while the intrinsic gamma luminosity of the BL Lacs has a negative correlation with the accretion disk magnetic field. A feedback effect may exist between accretion disk accretion rate and magnetic field, which may be the key to the evolution between BL Lacs and FSRQs. There is no significant difference in the jet power and jet generation efficiency of FSRQs and BL Lacs, which suggests that the jets are generated by the same mechanism. The contribution rate of accretion rate to jet generation efficiency is high, while the contribution rate of accretion rate to jet power is very low.