A high-capacity pulse tube cooler (PTC) with nominal cooling of 50 W/170 K is presented in this paper. It is driven by an opposed-piston dynamic magnetic linear compressor. The regenerator and pulse tube are arranged in coaxial. The inertance tube and reservoir are used as passive phase shifter of the PTC. Based on the principle of electrical-mechanical-acoustic coupling field, a dynamic model of the PTC is proposed and transient simulation was conducted on the characteristics of the compressor under load. The mass-spring system of the compressor is improved to make the PTC resonant. The mass of the PTC is less than 12 kg without electric control equipment. A performance of 50 W/170 K is achieved with 230 W electrical power while the motor efficiency and related Carnot efficiency are 92.7% and 16.5% respectively. The specific power (electrical power/cooling power) is less than 5 W/W at the temperature range of 150—200 K. Under the rated input power, the maximum cooling power reaches 90 W@200 K. The PTC can be used for space to cool down giant Infrared Focal Plane Array (IRFPA) and provide an alternative to domestic refrigerator as cold source at the temperature range of -60—-20℃ as well.