In modern era of computing every one wants a faster computing system. We can make it faster by improving hardware or by improving system software. Improving hardware may increase the cost of system so we can work on efficient software to boost the performance. Efficient Cache Replacement policy can improve the performance of operating system. In this book we have discussed in about memory hierarchy and cache replacement policy. In last section we have introduce a new replacement policy which works better than available one. We have include supporting work also. We have worked on combination of weight and rank parameter and concept of using extra buffer to increase hit ratio.