The “Hai Yang Shi You 123”FPSO crude oil cooler is a plate heat exchange, which normally operates with one in use and one as backup. As the oil production in the oilfield gradually increases， the load on the crude oil cooler gradually increases， resulting in poor heat exchange efficiency. Through physical property analysis of oilfield crude oil， the main reason for the poor heat exchange effect of the cooler is that the crude oil has a high wax content， a high wax precipitation point， and severe wax deposition on the side plate wall of the crude oil， which reduces the heat exchange capacity between the crude oil and seawater. To efficiently solve this problem， a comprehensive analysis was conducted on the equipment structure and process status of the crude oil cooler. A creative idea was proposed to optimize the two coolers into series operation， the application effect of the cooler series connection was verified on site， providing a reference for the stable operation of FPSO in the future.