The invention discloses a novel polymer water-based fire extinguishing agent and a preparation method thereof. The novel polymer water-based fire extinguishing agent is prepared from the following rawmaterials in parts by mass: 2-4 parts of ammonium polyphosphate, 6-8 parts of sodium carbonate, 6-8 parts of sodium silicate, 0.5-1 part of polyacrylamide, 2-4 parts of polyethylene glycol, 6-8 partsof sodium diethylhexyl sulfosuccinate, 12-16 parts of dodecyl betaine, 6-8 parts of sodium chloride, 5-9 parts of sodium benzoate, 7-13 parts of xanthan gum, 15-25 parts of n-butyl alcohol, 8-14 parts of a compound antifreeze agent, 8-10 parts of a foaming agent, 6-10 parts of an interface active agent, 8-14 parts of a surfactant and 80-100 parts of water. The novel polymer water-based fire extinguishing agent has the following beneficial effects that the oxygen isolation suffocation effect is obvious, components are mixing uniformly, the stability is good, precipitation cannot occur along with the change of the storage environment, the fire extinguishing effect is not affected after long-time storage, the proportion of all the components is optimized, the optimal synergistic effect is achieved, a water film can be formed on the surface of a comburent, oxygen is isolated, cooling, heat resistance and flame retardance are achieved, and extremely high flame retardance and after-combustion resistance are achieved.