Reducing CO2 emissions is a hot topic, and an important policy to achieve this target is carbon tax. When an enterprise is subject to a carbon tax, it has to pay this extra fee for the long-term if it does not upgrade its production technology. It needs to pay a certain upgrade fee in the short-term if it chooses to upgrade its plant. Thus, it has been an important problem for enterprises seeking to balance the trade-off between the 'long-term tax fee' and the 'short-term upgrade fee'. This paper explores how to optimise an enterprise's production technology upgrade strategy based on existing low-carbon technologies, to minimise the total upgrade cost subject to an expected total cost per product. An integer programming model is proposed to formulate the problem, and a 'multi-agent system - genetic algorithm' method is presented for its solution. The model is applied to a numerical example and the results indicate that the proposed method is feasible. The impacts of carbon tax and enterprise's expected cost on its technology upgrade strategy are further discussed. (C) 2017 Elsevier Ltd. All rights reserved.