An unfoldable portable pet bag has a bearing plate portion, extensible peripheral portion, lacing holes, control pull-cord, flexible portions and pulling and lifting portions. The portable pet bags can be unfolded and directly used as a mat for pets. Moreover, the unfoldable portable pet bag is flat when it is unfolded, enabling elimination of blind corners and making it easier for cleaning and drying. When pet owners plan to take pets with them, the pets could step into (or be carried into) the bearing plate portion. Next, the extensible peripheral portion can be quickly converged into a vertical framed body via upward pulling of said pulling and lifting portion. This could completely solve the problem of pets getting stuck when they're put into or taken out of the pet container, making it more convenient, quicker and safer to carry the pets with multiple functions.
