Restacking or aggregation inhibition of MXene nanosheets is crucial to the maintenance of their excellent electrochemical performance during use. In this study, a positively charged surfactant is inserted into the MXene nanolayers through a simple self-assembly process based on electrostatic interaction, producing a MXene/surfactant complex with enlarged interlayer spacing. Then 3D MXene-based porous structure could be prepared by the facile and low-cost breath figure method, in which MXene/surfactant complex is used as a casting material, therefore the inhibition of restacking or aggregation and increase of surface area at multiscale are realized in one system at the same time. Benefiting from the high conductivity of MXene and increased surface area of 3D porous structure that can provide massive active sites and facilitate the electrolyte infiltration and ion or electron access, enhanced electrochemical performance, for instance, electrochemical sensing of dopamine (DA) is shown. A low detection limit of 36.8 nM with excellent anti-interference, reproducibility, repeatability and long-term stability is realized. Good accuracy for DA detection in real biological samples is also confirmed by determining DA concentration in complex human urine samples. More importantly, porous structure such as pore size, uniformity, order and porosity can be adjusted through tuning the fabrication conditions, thereby regulating its electrochemical properties. This work not only provides a high-performance electrode for electrochemical sensing, but also offers a simple and practical strategy for the construction of 3D porous MXene film that holds great potential in electromagnetic interference shielding, supercapacitors and batteries.