A plant simulation model of SMR (single mixed refrigerant cycle) plant which considers the performance variations of devices under different working conditions is established. It could be used to predict the performance variations of an SMR plant under part-load, and other working conditions. The operational optimisation based on plant simulation is conducted for SMR plant with different load adjustment facilities. The constraint condition uses a penalty function method and the Box method is applied for solution optimisation. The results show that the frequency conversion method could achieve the best adjustment performance and the composition optimisation is significant for the frequency conversion method, especially when the load is below 40%. The operational strategy giving the lowest energy consumption for SMR plant with different adjustment methods under part-load conditions was discussed and the efficiency of the MR compressor is regarded as the prime influence thereon. (C) 2014 Elsevier Ltd. All rights reserved.