Abstract: While the strict integrity policy (SIP) of Biba's model can be used to maintain integrity of data in computer systems, the integrity labels of both subjects and objects in a system are always kept static in SIP, which might lead to denial to some non-malicious access requirements and hence decreases the compatibility o f applications. Dynamic enforcement of this policy (DESIP) is presented, which c an increase compatibility of software while keeping system integrity as strictly as SIP can. The implementation of DESIP is also given based on RFSOS, a Linux-b ased operating system, which shows that the impact of the enforcement of DESIP o n system efficiency is less than 1%.