The invention discloses a separation construction method for a mass concrete foundation unit. The separation construction method mainly comprises the steps of construction preparation, construction joint design, steel bar construction and formwork construction, concrete pouring construction, concrete press-polishing and curing, concrete temperature monitoring and the like. The separation construction method breaks the tradition that foundation mass concrete needs uninterrupted continuous construction day and night, the construction noise and light pollution disturbance, generated due to continuous concrete pouring at night, of community residents adjacent to a construction site are avoided, the traffic pressure caused by commodity concrete transportation in arterial streets during the morning and night travel peak period is reduced, and citizens are facilitated to travel; and meanwhile, the method is not limited by environmental protection inspection raw materials and commercial concrete supply, the foundation can be constructed in a segmented mode, the concrete supply problem is effectively solved, and the requirements of an environmental-friendly policy are well met.