The invention discloses a novel method for reducing nitrogen loss in composting process of perishable garbage. According to the novel method, biochar prepared at the high temperature of 800 DEG C canwell adsorb ammonium ions, so that volatilization of NH4 <+> in the composting process is reduced, and the nitrogen preservation process is promoted; the biochar is doped with certain iron ions, and iron-based biochar is added in the composting process, so that the generation of catalase in the aerobic biological reflection process can be promoted; the biochar adsorbs NH4 <+> in the reactor, the dissolution of NH4 <+> is inhibited, the formation of hydroxyl ions is prevented, and the increase amplitude of the pH value of the compost is effectively reduced; and by virtue of biochar, the nitrogen discharge in the composting process can be improved, and after the composting is finished, the biochar and the decomposed material after composting are applied to soil, so that the soil volume weight can be effectively reduced, the porosity is increased, the water holding capacity of the soil is improved, the field climate is improved, the field water holding rate is adjusted, the structure of the soil can be improved, the soil is loosened, the three-phase proportion of the soil is stabilized, and the pH value of the soil is improved.