During (partial) key escrow, monitoring is a vital phase. So how to monitor a us er safely and efficiently is a very important problem. According to the known mo nitoring schemes, after a user is monitored, his secret key is known. It is unfa ir to an honest user. In this paper, the authors propose a monitoring scheme of a typical partial key escrow scheme. In this scheme, the escrowed key of a user is not compromised even if the user has been monitored for many times.