Floating Production Storage and Offloading(FPSO) is an integrated, large-scale and mobile offshore oil and gas production facility that is normally moored in fixed sea area over a long period of time. As a core element of the offshore oil and gas development, FPSO integrates the offshore oil and gas production and processing, storage and offloading, power supply and living support. With these obvious advantages, FPSO has been deployed more and more widely in offshore oil and gas field development. The construction of FPSO is complex and difficult, and the equipment and facilities of the FPSO have a high degree of module integration. As a result, the construction duration of FPSO could be quite long. An accurate and reasonable evaluation of FPSO construction duration has direct impact on the start-up date of oil and gas fields as well as the overall development plan, so it is very important to the progress control of offshore engineering projects. The construction duration of FPSO is related to many factors. This paper summarized the general process and approaches of FPSO construction and integration, and analyzed the overall construction duration for FPSO with the critical path method. On this basis, this paper put forward an evaluation method for FPSO construction. This method is verified by an actual engineering example, and it concludes that this method can be used in large FPSO construction and integration planning and construction duration evaluation. The research results could provide a reference for similar FPSO construction and integration planning and construction duration evaluation.