The invention relates to a foam plugging type microbial decomposition water circulating environmental protection toilet for islands. A process for treating liquid dung comprises the following steps of: allowing excrement and urine which are washed by foam to enter a biochemical box to perform primary treatment, separating and depositing to remove foreign matters and impurities in water, and regulating the liquid dung; allowing the liquid dung to enter anaerobic and aerobic biochemical systems to perform secondary treatment, and adding microbial strains special for excrement degradation, so that most of organic matters in sewage are decomposed gradually to form colourless and inodorous gas and trace inorganic matters, and the water quality is purified; and finally, performing tertiary treatment on the water, and removing chromaticity, odor, germs and the like in the water through filtering, aeration, adsorption and micro-filtration. In the foam plugging type microbial decomposition water circulating environmental protection toilet, microbes can decompose the excrement completely so as to meet requirements of non-pollution discharge and no need of sewage pipelines, the excrement can be decomposed in about 20 hours, the decomposition rate is over 90 percent, and decomposition products are water vapor, carbon dioxide, organic acid and the like; and the toilet can improve the environment obviously and has the obvious economic and social benefits.