The present invention discloses a flexible wearable strain sensor based on fabrics and a preparation method thereof. Fabrics are taken as raw materials; carbonization fabrics capable of keeping the structure of original fabrics and having flexibility and electrical conductivity in the high-temperature heat treatment process in the atmosphere of taking inert atmosphere or inert gases as the principal thing; two ends of the carbonization fabrics are connected wires or integration wireless emission receiving module; and a flexible wearable strain sensor is obtained through package by using elastomeric polymers. The flexible wearable strain sensor based on fabrics are able to directly attach to the skin, the clothes or other wearable accessories to realize the wearable detection of human joint movement, pulse, microexpression, breath, sound production or audio frequency. The flexible wearable strain sensor based on fabrics and the technological process of production thereof are sustainable in development, simple in preparation, low in cost, good in flexibility, wide in strain detection range, high in sensitivity, short in response time, good in cycling stability and durability, and broad in application prospect.