Fouling is a crucial problem in refinery HEN (heat exchanger network) that reduces heat transfer and affects regular production. The conventional way to mitigate fouling is cleaning heat exchanger regularly or improving operation conditions, but simultaneous consideration of the two methods is rare. This paper presents a combined approach for mitigating fouling in HEN by optimizing operation condition and cleaning schedule simultaneously. For optimization of operation condition, flow velocity is selected as a key variable since it can correlate fouling, heat transfer and pressure drop. An overall optimization of network performance can be achieved through redistribution of velocity. In a refinery HEN, fouling cannot be completely prevented through optimization of operation conditions, so management of cleaning actions is optimized to deal with the remained fouling. SA (Simulated annealing) algorithm is used in this work to obtain a comprehensive strategy for mitigating fouling. The application of the proposed method is demonstrated using a case study. The results show higher energy saving and economic efficiency compared with existing methods. (C) 2016 Elsevier Ltd. All rights reserved.