During the post quantum era, public key cryptosystem based on Lattice is considered to be the most promising cryptosystem to resist quantum computer attack. Comparing to the rapid development of public key encryption and digital signature schemes based on Lattice, the key agreement protocols rarely appeared in the research papers. Therefore, how to construct the secure key agreement protocol is one of the most challenging problems. To solve this problem above, a secure key agreement protocol RAKA based on reconciliation technique and ring learning with errors (Ring-LWE) is designed. The proposed scheme is provably secure under the Ring-LWE assumption and can provide authentication by using the Lattice-based trapdoor function. Compared with current key agreement schemes based on LWE, this scheme is more efficient and the shared key size is reduced to 2nlogq. Moreover, this scheme can resist quantum attack because of the hard assumption on Lattice.