The invention provides a dry construction method for a closed seawater source heat pump system. The method comprises the following steps that in the tide falling process of seawater, the thickness ofa sandy soil layer is measured, and the height of a caisson is determined according to the thickness of the sandy soil layer; according to the height of the caisson, a caisson module is processed andmanufactured, and a capillary network in the caisson is arranged so as to complete the preparation of the capillary network caisson; the tide falling time and the tide rising time of the seawater arecounted and are compared with the tide time of the seawater so as to obtain the construction time; earth excavation is carried out according to the construction time, and a water collecting and distributing device and part of collecting pipes are pre-buried in advance; a foundation pit is excavated according to the construction time, and the capillary network caisson is hoisted and buried; and thecapillary network caisson is connected to the collecting pipes, and a hydrostatic test is carried out so as to complete dry construction of the closed seawater source heat pump system.