The invention provides an in-situ comparison analysis method for rock mineral components before and after CO2 water-rock interaction. The invention also provides a protection device used for a high-temperature high-pressure sample and used in the method. The device includes a stainless steel sample clamp and an elastic sheath which have hollow cylindric structures. The elastic sheath is disposed in the stainless steel sample clamp. The method can achieve in-situ quantitative evaluation and search for rock mineral components before and after CO2 water-rock interaction. Three representation manners are adopted for corroboration for each other so that the method is direct and visual and effectively increases mineral research precision. The device and the method effectively make up a weaknessthat present experimental techniques cannot achieve in-situ comparison for mineral components before and after interaction, and can provide important models for CO2 mineral conversion, CO2 geologicalembedding and storage mechanism studying and numerical simulation, thus further promoting laboratory basic research.