Along with the position of knowledge learning is more and more important and artificial intelligence technology continues to evolve, there is a lot of software for knowledge learning. However, the software is not able to accurately grasp the essence of the knowledge learning, these software did not deeply dig the human brain and the relationship between memory and forgetting, so they cannot use human brain"s memory character to help people remember knowledge fastly and effectively. Therefore, an intelligent knowledge learning expert system which can effectively improve word memory is necessary. I take the English word for knowledge learning"s example. In this paper, through the research of memoryforgetting principle and the association mode in human brain, expounded memoryforgetting mode and word network associated graph, demonstrated its effectiveness of the word memory, in this paper, finally, came to the English learning expert system based on memory-forgetting model and association mode. © Springer-Verlag Berlin Heidelberg 2014.