At present, there is a tendency to develop oil and gas fields with unmanned and lightly manned operating facilities, especially for small marginal oil and gas fields. The displacement procedure of the oil and gas pipeline for unmanned offshore platform has a direct impact on the operation safety of the pipeline. Bohai oilfield explores with a great deal of schemes and procedures in the displacement of the subsea pipeline for the unmanned platforms. Different displacement methods have been formulated with varying procedures and reliability; and each scheme has its own favourable conditions and application scope. Among them, the cyclic displacement is mainly used in the waterflood development or the depleted marginal field development with high gas-oil ratio (GOR); while the forward displacement and reverse displacement are mainly applied in the depleted marginal field development with low GOR. In practice, the optimal displacement scheme should be determined by comprehensive comparison of operational convenience, economics aspects and technical maturity, incorporating factors such as availability of supporting facilities around the oil field, process scheme of unmanned platform, oil and gas physical properties and the length of subsea pipeline. The formed replacement schemes ensure the operation of unmanned platform oil and gas subsea pipeline safely and promote the effective development of marginal oil fields in the Bohai Bay.