The invention discloses a process device and a process method for recovering cold energy from LNG prepared from coke oven gas. The device comprises a dehydrogenation tower, an LNG reflux pump, a coaxial compression expander, a liquid separation tank and a heat exchanger, wherein the heat exchanger is sequentially connected with the dehydrogenation tower, the LNG reflux pump, the coaxial compression expander and the liquid separation tank; and a feed port at the top of the dehydrogenation tower is sequentially connected with the heat exchanger and the LNG reflux pump. The process device and the process method disclosed by the invention have the beneficial effects that hydrogen-rich gas cold energy recycling and expander refrigeration are adopted to recycle the cold energy from a device for LNG prepared from the coke oven gas; part of the cold energy is provided for LNG and a mixed refrigerant by use of low-temperature hydrogen-rich gas removed from the coke oven gas; and meanwhile, reheated hydrogen-rich gas enters the heat exchanger again by throttling expansion to provide the cold energy until the hydrogen-rich gas enters the coaxial compression expander at normal temperature. The process device is simple in flow; the corresponding heat exchanger is only additionally provided with two flow channels, and the simplicity in operation is realized, power consumption of a refrigerant compressor unit can be greatly saved; and the hydrogen-rich gas can be flexibly disposed according to the downstream demand.