Abstract: The construction sequence of backfill soil and mixing piles on the site will directly affect the treatment effect of the soft ground composite foundation, and the settlement control is the key to the safe operation of the soft ground floor. Taking the composite foundation engineering of cement-soil mixing piles for industrial plants in offshore soft soil areas as an example, the influencing factors and settlement differences of two different construction sequences of composite foundation cement-soil mixing piles and backfilling soil are discussed. Total settlement, construction settlement and post-settlement of foundation consolidation under two conditions are calculated and analyzed through numerical simulation tests. The results show that the settlement during construction by using the construction sequence of "backfill soil first, then pile" is greater than the "pile first, then backfill soil", but the settlement after construction is greatly reduced, which improves the effect of soft ground foundation treatment and is beneficial to the safety of the soft ground after treatment. The foregoing analysis conclusions is verified by the operation, which provides an important reference for determining a reasonable design scheme.