A dynamic password security login method is provided, which sets that a client and a server have weight synchronous models with the same parameters, and comprises the following steps: initiating a login request by the client, and sending a user name to the server, generating a random number by the server and returning to the client, obtaining that M=user 'Passwd' R, H=SHA1(M), F=LFSR (H) by respective calculations of the client and the server, obtaining the same weight WC=WS according to the mapping algorithm of a random number sequence F, leading the weight synchronous model to study P=%n order by the client according to the random number, wherein R is the random number, n is a preset value, sending the weight vector WC after updating P orders to the server after Hash algorithm SHA1(WC), and leading the weight synchronous model to study P orders by the server to obtain the weight vector WS after updating P orders, and calculating the Hash value SHA1 (WS) thereof, wherein the identification is success if the SHA1 (SC)=SHA1(WS), or is false. The dynamic password security login method has simple use, highly-effective security and low cost.