An apparatus for gas-liquid separation, the apparatus comprising: a cyclonic fluid generation section, a fluid conversion section and a fluid separation section having a same central axis and being connected in sequence along said central axis; the cyclonic fluid generation section being for receiving a gas fluid and providing a cyclonic fluid by accelerating the gas fluid to reach the velocity of sound, so that a portion of or most of the gas fluid is converted to a gaseous vortex; the fluid conversion section being for receiving the cyclonic fluid and providing a liquid fluid and having a minimum tube diameter among all sections of the apparatus along the central axis, such that a change in tube diameter from the cyclonic fluid generation section to the fluid conversion section decreases the static temperature of the gaseous vortex that keeps flowing at the velocity of sound to a condensation point of a gaseous component generating the liquid fluid; and the fluid separation section comprising: a first fluid passage for receiving the liquid fluid; and a second fluid passage for receiving the gas fluid that is not converted to be the liquid fluid, the second fluid passage having the same central axis as the fluid conversion region and presenting a continuous tubular structure on the central axis, the first fluid passage being formed on an outer side wall of the second fluid passage, a liquid fluid exit being formed at one end of the first fluid passage to discharge the liquid fluid and a gaseous fluid exit being formed at one opening of the second fluid passage to discharge the gaseous fluid; wherein the second fluid passage is elliptical in cross-section; wherein a transversal cross-section of the fluid separation section has a first width and a second width, the first width is larger than the second width and is a maximum width of the cross-section of the fluid separation section, and characterized in that the first fluid passage is communicated with the second fluid passage where the first maximum width is, wherein the first fluid passage extends outwards from the outer surface of the second fluid passage and the first fluid passage presents a branch structure extending from front and tail ends of the first maximum width of the fluid separation section. a cyclonic fluid generation section, a fluid conversion section and a fluid separation section having a same central axis and being connected in sequence along said central axis; the cyclonic fluid generation section being for receiving a gas fluid and providing a cyclonic fluid by accelerating the gas fluid to reach the velocity of sound, so that a portion of or most of the gas fluid is converted to a gaseous vortex; the fluid conversion section being for receiving the cyclonic fluid and providing a liquid fluid and having a minimum tube diameter among all sections of the apparatus along the central axis, such that a change in tube diameter from the cyclonic fluid generation section to the fluid conversion section decreases the static temperature of the gaseous vortex that keeps flowing at the velocity of sound to a condensation point of a gaseous component generating the liquid fluid; and the fluid separation section comprising: a first fluid passage for receiving the liquid fluid; and a second fluid passage for receiving the gas fluid that is not converted to be the liquid fluid, the second fluid passage having the same central axis as the fluid conversion region and presenting a continuous tubular structure on the central axis, the first fluid passage being formed on an outer side wall of the second fluid passage, a liquid fluid exit being formed at one end of the first fluid passage to discharge the liquid fluid and a gaseous fluid exit being formed at one opening of the second fluid passage to discharge the gaseous fluid; wherein the second fluid passage is elliptical in cross-section; wherein a transversal cross-section of the fluid separation section has a first width and a second width, the first width is larger than the second width and is a maximum width of the cross-section of the fluid separation section, and characterized in that the first fluid passage is communicated with the second fluid passage where the first maximum width is, wherein the first fluid passage extends outwards from the outer surface of the second fluid passage and the first fluid passage presents a branch structure extending from front and tail ends of the first maximum width of the fluid separation section.