A new algorithm based on orthogonal projector for transmission line transients is proposed. By the new method， which utilizes function approaches theory， projection operator theory and multi-resolution analysis， the telegraphic equation can be projected into a function space， which is spanned by the orthogonal basis function relates to variable t in an given binary resolution， and then an vector equation with only one variable of distance x is presented. By solving the vector equation the new algorithm for transient computation and analysis is constructed. Through the EMTP simulation tests， it is proved that the new algorithm is correct and accuracy. The new approach can overcome two drawbacks of the traditional Characteristic Method. Meanwhile， the prospect based on this method is described.