  We propose a new Quantum Key Recycling (QKR) protocol, which can tolerate the
noise in the quantum channel. Our QKR protocol recycles the used keys according
to the error rate. The key recycling rate of the pre-shared keys in our QKR
protocol is optimized depending on the real error rate in the quantum channel.
And our QKR protocol has higher efficiency than the exiting QKR protocol with
error-tolerance. The security proof shows the security of the recycled keys is
universal composable.
