NOVELTY - Use of alkali substance-based pepper extract as a pesticide synergistic agent, is claimed.    USE - The extract is useful as a pesticide synergistic agent, preferably plant-derived pesticide in an organic food production chain (all claimed).    ADVANTAGE - The extract has plant resources which is natural, pollution-free, and non-toxic to humans and the environment, and increased pesticidal efficiency of 10.6-30.2%, and natural pyrethrin which increases the pesticidal efficacy up to 24.5-30.2%.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for preparing alkali substance-based pepper extract, comprising (i) drying the immature pepper seed, crushing to a particle size of 5-40 meshes, placing in an extracting tank, starting the stirring process, stacking the material flat into a kettle, and adjusting the degree of vacuum in a extraction tank to 0.02-0.08 MPa by opening a vacuum pump, injecting sub-critical liquid R134a as a solvent, and mixing the raw materials until the liquid level has reached higher level, and extracting under controlled temperature of 30-60 degrees C, and pressure of 0.3-1 MPa, and soaking while extracting for 30-180 minutes, and simultaneously carrying out ultrasonic processing while soaking and extracting, where processing time is 1-7 minutes at an interval of 2-10 minutes, and repeatedly circulating, and completing the extraction, terminating the ultrasound processing step, separating solid-liquid phase, conveying the liquid phase in the mixed liquid into a storage tank, and adding a solvent into the solid-phase waste slag, and repeating the soaking-extraction processes, ultrasonically separating the solid-liquid phase, and repeating the extraction process for 3-6 times, each time soaking-extracting for 10-60 minutes; (ii) pumping solvent under certain pressure, auto-cleaning the mixed liquid in a liquid storage tank, filtering, and pressing by a one-level analytical kettle, repeatedly passing the liquid mixture through a tube-type heat exchanger, under pressure of 0.3-1 MPa at 30-60 degrees C, and evaporating solvent from the liquid phase mixture by conveying into a solvent recovery system, and allowing the liquid extracts to stand in a primary reactor, and completing first-stage analytical process once the pressure of the liquid level in the analytical kettle autoclave reached 0.1-0.2 MPa; (iv) conveying the primarily separated liquid extract from first-stage analytical kettle into a second-stage analytical kettle, and conveying the liquid extract from the top part of the kettle to form small droplets by spray diffusion process at 30-60 degrees C at pressure of 0.3-1 MPa, and conveying the remaining tiny droplets of solvent downwards through a jacket-type heat exchanger, and evaporating; and (v) conveying the extract from the second-stage analytical kettle into an extract storage tank by a pump, to obtain the final product.