The invention discloses a Byzantium fault-tolerant consensus optimization method for a block chain. The method comprises the following steps: S1, performing voting weight table initialization; S2, processing transaction; S3, electing a main node; S4, verifying a REQUEST message; S5, broadcasting a PRE-PREPARE message; S6, verifying the PRE-PREPARE message; S7, performing voting; S8, broadcasting the PREPARE message containing a voting value; S9, recording the message and the number of voting to a local log; S10, performing weighted sum on the voting value, and performing nonlinear processing;S11, broadcasting the COMMIT message; S12, verifying the COMMIT message; S13, writing the current block into a local account book, and replying a client. The problem that the method disclosed by the invention is limited in application scene, low in security, needs to consume a large amount of communication resources and is large in system resource consumption in the prior art is solved.