To improve the efficiency of knowledge work, an optimization method, mining experts' implicit knowledge is proposed. The valuable implicit knowledge is mined from the experts, and then the corresponding model of work steps and related implicit knowledge is established. Considered the specialty of implicit knowledge existed in different practical activities, an experiment about dimension design based on the secondary development of ANSYS is performed. The experts' implicit knowledge work is externalized with methods of think-aloud protocols and observations. At last, comparative experiments are designed to analyze the optimization effect, and the result indicates that the externalized knowledge has obvious contribution to the knowledge work optimization. Keywords implicit knowledge, knowledge externalization, knowledge work, knowledge mining ___________________________________ 978-1-61284-449-7/11/$26.00 ©2011 IEEE