NOVELTY - Preparing emergency water under emergency condition using wastewater comprises (i) prefiltering using a prefilter, where the prefilter comprises a first container, a filter material and a second container,; (ii) carrying out flocculation and precipitation by adding edible vinegar and bleaching agent into the wastewater, stirring, precipitating the clay colloid and mineral in the wastewater, and removing hydrogen sulfide and methane; and (iii) filtering by a filtering device, where the filtering device comprises a simple filter, a plastic bag and a collecting container.    USE - The method is useful for preparing emergency water under emergency condition using wastewater (claimed).    ADVANTAGE - The method: ensures simple and fast (claimed) processing when natural disasters including earthquake, flood and typhoon occurs suddenly; is convenient to operate, utilizes materials which are easily available, and utilizes device which can be built easily; and ensures good wastewater treatment effect, achieves repeated use, is environmentally friendly and economical.    DETAILED DESCRIPTION - Preparing emergency water under emergency condition using wastewater comprises (i) prefiltering using a prefilter, where the prefilter comprises a first container, a filter material and a second container, the filter material is placed above the second container and a second container port covers the layer of the filter material, the first container is placed above the filter material so that the bottom hole of the first container is in contact with the filter material, the central line of the first container and the second container are axially arranged, the wastewater is injected into the first container, the injected wastewater is percolated into the second container via the filter material to obtain the primary filtered water, which is free from large particles, suspended sediment substances and parasites; (ii) carrying out flocculation and precipitation by adding edible vinegar and bleaching agent into the wastewater, stirring, precipitating the clay colloid and mineral in the wastewater, and removing hydrogen sulfide and methane with peculiar smell gas in the wastewater; and (iii) filtering by a filtering device, where the filtering device comprises a simple filter, a plastic bag and a collecting container, the bottom of the plastic bag covering the simple filter is provided with a guide device, the other end of the plastic bag is introduced into the collecting container, where in the step (ii) the processed wastewater is introduced into a filtering device for removing sediments and color.