Abstract: It was found that on access which causes the conflict between parallel applications and shared cache will lead the system performance to degrade for the multi-core processor involving a shared cache. To solve the problem efficiently and reasonably, allocation algorithm is proposed for the shared cache, i.e., sorting and tracking the cases the parallel applications are missing the access as a target to shared cache, then the shared cache is allocated dynamically for cache's line granularity according to the performance gain model developed to improve the system performance. Testing results showed that the new algorithm is able to reduce the conflicting accesses and enable the system to achieve better performance and higher processing efficiency by allocating the shared cache to the parallel operations on multi-core processor reasonably.