To meet the changes of internal and external environment, Enterprise Resources Planning (ERP) system needs to have a good flexibility. Flexibility is an indispensable request and is also a way that must be taken during the establishment process of ERP. Flexibility measurement is an important item for the implementation of ERP flexibility. According to the characteristics of ERP system, an index system for flexibility measurement of ERP system is presented with the interdependence and feedback relationships among criteria and/or indices being taken into account. Due to the vagueness and uncertainty information during the process of flexibility measurement, triangular fuzzy numbers are used to indicate the preference opinions of experts and decision makers. A flexibility measurement model of ERP system based on fuzzy analytic network process (FANP) is proposed. The local weights of criteria and indices are derived by fuzzy preference programming (FPP) method. An unweighted supermatrix based on the network structure of index system is developed, and the limit supermatrix is generated. The flexibility level of ERP system can be measured by the weights and scores of ERP. Finally, a case is given by the proposed method. © 2013 ACADEMY PUBLISHER.