This document proposes i2MapReduce, a novel incremental processing expansion to the MapReduce framework for data mining big data. i2MapReduce executes fine-grained incremental processing at the key-value pair level to refresh mining results, unlike existing approaches that use task-level recomputation. It incorporates techniques to reduce I/O for accessing computation states. Experimental results on Amazon EC2 show i2MapReduce significantly improves performance over iterative and plain MapReduce that perform full recomputation when data changes.