There exist uncertain factors in power systems

and the development of the smart grid has brought about more uncertainties to power systems. The traditional transmission network planning methods are not adapted to transmission system planning in the new situation. In order to make planning schemes adaptable to the effects of uncertainties

uncertainty theories have been introduced into transmission network planning with success. From the perspective of random theory

fuzzy set theory

credibility theory and whatnot the domestic and international achievements in modeling methods of uncertainties and uncertainty theories based transmission system planning approaches are reviewed. In terms of fast calculation for evaluation indices

processing methods for uncertainties and so forth

problems to be noticed and suggestions for future research on the uncertainty theory based transmission network planning are put forward. This work is supported by National Natural Science Foundation of China(No. 51337005)and State Grid Corporation of China(No. XT71-14-002).