A biocompatible oil-in-water emulsion containing no surfactant or other organic modifier was prepared using two negatively charged, naturally derived materials: alginate and montmorillonite (MMT), and it was found that the stable emulsion has good storage stability and coalescence stability. The dispersing and suspending effects of alginate to MMT were observed, and the interaction between alginate and MMT was confirmed by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and Zeta potential. The distribution of particles at the oil-water interface and in the aqueous phase of the emulsion was observed by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). A unique mechanism of the stable Pickering emulsion was then proposed. It is demonstrated that alginate not only thicken the continuous phase, create a gel-like environment around the droplets, but also could modify the MMT surface, synergistically enhance the electrostatic force of droplets due to the same charge property with MMT. Moreover, the rheological properties of the emulsion co-stabilized by MMT/Alginate can be well adjusted using various stimuli including pH and salt. In general, this work presents a highly stable, tunable and biocompatible emulsion for potential applications in food and cosmetic products. (C) 2019 Elsevier Inc. All rights reserved.