Run jupyter kernelspec list to get the paths of all your kernels.
Then simply uninstall your unwanted-kernel
jupyter kernelspec uninstall unwanted-kernel
Old answer
Delete the folder corresponding to the kernel you want to remove.
文档中有一个存储内核的公共路径列表:http://jupyter-client.readthedocs.io/en/latest/kernels.html#kernelspecs