This article suggests a comprehensive analysis of the complex speech genres as a way to study the variability of their model and as an instrument of developing the general classification of complex speech genres. The lack of a unified classification of speech genres, the use of the concept of speech genre as a multidisciplinary, globalization, vanishing of their national features, the emergence of new genres in electronic communication, the erosion of the images of genres – all these phenomena indicate the necessity of creating system, which could structure the study of genres. The article proves the feasibility to solve this problem using terminology of the four bases spheres: theory of genres, linguistics, pragmalinguistics and cognitive linguistics. From this standpoint, linguistic and cognitive analysis of speech genre is a procedure for identifying field of variability of the main model of this genre, depending on the history of its formation (whether the genre borrowing, as the essay in Russian culture, does it depend on the type of real/virtual sphere, etc.) and the specific intersections of such categories as type of concept, type of mental spaces, type of speech strategies, type of reference, type of the modal subject. In addition, the author believes that the characteristics of the overall image of the speech genre is determined by its associating with one of the five pictures of the world: mythological, religious, scientific or naive. In this regard, the author distinguishes the stylistically non-transient and transient speech genres. An example of the analysis of variability of Russian-speaking essay as one of the most complex, stylistically transitional, not having a rigid structure of speech genres is given to prove the validity of the system.