Abstract: The size of proxy signature secret key in proxy signature scheme based on lattice basis delegation in fixed dimension or bonsai tree is greater than that of original signature secret key. Aiming at the situation above, a new efficient proxy signature scheme is proposed. The random oracles are combined in the scheme and a smaller vector norm blind message is used to control the dimension of proxy signature secret key. The security of proposed scheme is based on the hardness of shortest vector problem and small integer solution problem, and the scheme satisfies the security requirements of a proxy signature scheme. Compared with other schemes over lattice, the size of proxy signature secret key and proxy signature is reduced, and the size of proxy signature secret key is equivalent to that of the original signature secret key in magnitude.