NOVELTY - Microorganism-derived virus-resisting agent comprises 10-30 wt.% Omphalia lapidescens Schroet extract as active ingredient, 30-60 wt.% organic solvent, 5-30 wt.% surfactant, 4-10 wt.% antifreezing agent, and water (remainder). The agent is prepared in the form of soluble liquid agent or microemulsion. The microemulsion comprises 10-30 wt.% O.lapidescens extract, 30-60 wt.% organic solvent, 5-30 wt.% surfactant, 4-10 wt.% antifreezing agent, and water (remainder).    USE - The microorganism-derived agent is useful for controlling tobacco mosaic virus (TMV) diseases, cucumber mosaic virus (CMV) diseases, potato virus X and Y (PVX and PVY) diseases and other several plant virus diseases with respect to tobaccos, chilies, tomatoes, vegetable marrows, potatoes and other crops.    ADVANTAGE - The agent has favorable virus-resisting effect, and is safe to the environment, humans, livestock, natural enemies of pests and other beneficial organisms. The preparation process of the agent is simple, cost-effective and suitable for popularization.    DETAILED DESCRIPTION - Microorganism-derived virus-resisting agent comprises 10-30 wt.% Omphalia lapidescens Schroet extract as active ingredient, 30-60 wt.% organic solvent, 5-30 wt.% surfactant, 4-10 wt.% antifreezing agent, and water (remainder). The agent is prepared in the form of soluble liquid agent or microemulsion. The microemulsion comprises 10-30 wt.% O.lapidescens extract, 30-60 wt.% organic solvent, 5-30 wt.% surfactant, 4-10 wt.% antifreezing agent, and water (remainder). The soluble liquid comprises 0-30 wt.% O.lapidescens extract, 30-60 wt.% organic solvent, and 5-30 wt.% surfactant.    An INDEPENDENT CLAIM is included for method for preparing the above-mentioned agent, which involves (a) crushing O.lapidescens plant tissue to particle diameter of 1-5 mm, subjecting the pulverized product to solvent extraction process using ethanol, ethyl acetate, chloroform, petroleum ether and/or water at 50-80 degrees C for 6-12 hours, and concentrating the obtained extract to 1 kg dry powder, and (b) (i) adding the dry powder, organic solvent and surfactant to a mixing kettle, mixing at 35-60 degrees C, and stirring for 30 minutes uniformly to obtain microemulsion, (ii) adding antifreezing agent, organic solvent and surfactant and the dry powder to the reaction kettle, mixing the obtained mixture at 35-60 degrees C, and stirring for 30 minutes uniformly to obtain soluble liquid agent, or (iii) adding antifreezing agent, organic solvent and surfactant and the dry powder to the reaction kettle, stirring at 35-60 degrees C for 30 minutes uniformly to obtain pill.