Address assignment mechanisms (AAM) packet validation, binding entry updating and denial of service (DoS) attack mitigation were considered to improve the safety of IPv6 source address validation improvement (SAVI) binding table in software defined network (SDN). AAM packet validating table is established in SDN controller to record switch port, MAC address and host address. AAM packet validation procedure for DHCPv6 and SLAAC is built, which sends out flow rules for router advertisement (RA) snooping to collect DHCPv6 request/reply packets and NS/NA packets, and verifies IP address in these packets based on AAM packet validating table. The monitoring and updating mechanism of binding entries is established to adapt to dynamic network, in order to detect events such as host offline and IP failure, update binding table in time and ensure consistency between SAVI binding table and actual network information. The traffic rate limiting table of switch port is set up based on the Openflow muti-level flow table to defend against DoS attack. Experimental results show that the proposed procedure can mitigate various attacks which forge AAM packets to break SAVI binding table, update SAVI binding table records in time and improve AAM packets processing efficiency.