Abstract: An algorithm of cryptographic hash function based on time-delay chaotic system is presented in this paper. In this algorithm, initial message is modulated into time-delay chaotic iteration, and the Hash value can be calculated by a HMAC-MD5 algorithm. Thus, every bit of this Hash value is correlative with initial message,and this Hash value is very sensitive to micro changes of the initial message or the initial condition of chaotic system. By theory analyses and simulations, we obtain that the Hash value has irregularity and diffusion properties, and the parameter space is augmented because of the properties of chaos. The nonlinear relation between hash value and initial message can be effectively against linear analysis. Therefore, this Hash function based on time-delay chaotic system can get better anti-attack and anti-collision capacity.