The invention relates to an emergency well closing device and an emergency well closing method for out-of-control blowout in deepwater drilling. The device comprises a plurality of underwater well closing device module groups. Each underwater well closing module group comprises a connector, a four-way joint, flow barrier modules, a short connecting part, an upper joint and a throttling well control module, wherein the connector, the four-way joint, the flow barrier modules, the short connecting part and the upper joint form a main passage, the bottom of the connector is used for connection with an accidental well, the four-way joint is arranged at the top of the connector and connected with the bottom of one of the flow barrier modules and the throttling well control module, the top of the flow barrier module is connected with the bottom of the other flow barrier module through the short connecting part, and the top of the other flow barrier module is connected with the upper joint. Underwater well closing devices can be transported to the accidental well in short time to realize well closing, so that loss caused by blowout can be reduced. The emergency well closing device and the emergency well closing method can be applied to emergency rescue after failure of underwater well control measures.