Abstract: A scheme for solving the security threat to mobile agent (MA) in malicious hosts was proposed based on asymmetricalencryption. In the scheme, only can the hosts thatgetpermissions run the codes ofMA, and data for exchanging are also encrypted. After returning to the source hos,t MA checks the data ithas collected to ascertain if ithas been attacked. The security threats thatMA may encounter inmalicioushostswere analyzed one by one, and each of them was solvedwith the proposed scheme.