Composition and monitoring content of condition monitoring and faults diagnosis are described in this paper.Some existing methods of dielectric loss are analyzed and compared.Some problems needing attention are analyzed in detail.The performance of sensor should be improved.The fault diagnosis technology should be closely associated with some new mathematical tools.It is emphatically pointed out that the research emphasis is studying on new algorithm comprehensively considering eliminating harmonic influence

frequency fluctuating

asynchronous sampling and non-integer period sampling

and so on.Thinking mode of laying stress on practicality and ignoring basic research should be changed.Basic theory should be done thorough research in the future.