Compared with conventional reservoirs, complex reservoirs often have more variety of pore types and more complex pore shape. For example, carbonate rocks can have a variety of pore types, such as moldic, vuggy, interparticle, intraparticle and crack. Therefore the essential of rock physics modelling of complex reservoirs is to characterize the complicated pore structure, that is to say, the rock physics model can contain a variety of pore types. This paper selected the critical porosity model as the study object, by combining with Kuster-Toksoz equations, established the relationship between the critical porosity of rocks and the pore structure (i.e. the pore aspect ratio) of rocks, proposed a new model named multiple-porosity variable critical porosity model which can contain various pore types and can be used to model complex reservoirs.