By understanding the core technologies such as asymmetric encryption, distributed storage, timestamp and consensus mechanism of block chain, this paper creates the trust by relying on technology and applies it to after‐sales service platform. At the same time, we use the characteristics of block chain technology, such as decentralization, openness, transparency, security independence, and marks on the chain, to achieve the accuracy, security and authenticity of after‐sales service, hoping to bring some enlightenment to the construction of after‐sales service platform in China.