A soft X-ray light source, including a vacuum target chamber, a refrigeration cavity, and a nozzle. The refrigeration cavity and the nozzle are contained in the vacuum target chamber. The nozzle (36) is arranged in the refrigeration cavity. The vacuum target chamber has a t-branch tube and a multi-channel tube. The t-branch tube has a first outlet and a second outlet opposed to each other and a third outlet, wherein the first outlet is connected to a mounting plate through which a refrigerant inlet pipe, a refrigerant outlet pipe, and a working gas pipe respectively pass and are connected to the refrigeration cavity, and wherein the third outlet is connected to a vacuum extraction device. The multi-channel tube has a top opening and a bottom opening opposed to each other, wherein the top opening is connected to the second outlet, wherein a vacuum outlet is provided at the bottom opening.