Abstract: The offshore unconsolidated sandstone reservoirs in Shengli are characterized as having multiple oil layers, long well sections, thick interlayers, strong inter-layer heterogeneity, and easy sand production. Electric submersible pumps are used for commingling production with overall sand control, accompanied by prominent inter-layer contradictions, but they cannot give full play to each producing layer and restrict the development of offshore oil fields. Therefore, separate layer sand control and oil production technology for the offshore unconsolidated sandstone reservoirs was studied. Considering the loose compaction of packing and small diameter after overall sand control, a large diameter separate layer packing sand control method was developed. With the method, separate layer sand control was achieved and the diameter was enlarged for following separate layer oil production. In addition, an oil and water swelling packer, and an online electric regulating valve were developed. A separate layer production technology was then formed, with which the separate layer production and online regulation of the flow from each layer were realized. The separate layer sand control test was done on Well 20C-A of Chengbei Sag offshore, resulting in differentiable packing sand control and thus exploiting the potential of production for each layer. The separate layer production tests were conducted on GO2-17-A and GO4-19-B onshore, for they have the similar formation physical properties and the same size of completion tools for oil wells of the offshore unconsolidated sandstone reservoirs in Shengli. Both the wells achieved separate layer oil production and accurate regulation of liquid-producing capacity for each layer, with increasing oil production and decreasing water content. The field application shows that the technology has solved the prominent inter-layer contradictions in commingling production of offshore unconsolidated sandstone reservoirs, and it can fully exploit the production potential of each layer, which resulted in oil production improvement.