Making use of the classical principal-agent theory,this paper unveil the internal mechanism of the price contracts of technology licensing under the conditions of adverse selection.This paper show that it can differentiate between the good-type and bad-type technology licensee through the royalty contracts for the bad licensee.Because the good-type licensee is efficient,the contracts is always a pure fixed fee contracts regardless of conditions.But under the conditions of adverse selection,the technology licensor must pay some information rent for the good licensee.