A reaction chamber for Metal-Organic Chemical Vapor Deposition, MOCVD, comprising: a chamber body, the chamber body being grounded; an upper cover, the upper cover being provided with an electrode, the chamber body being connected to the upper cover through an insulation member, the chamber body and the upper cover forming an inner chamber, and a through-hole communicating with the inner chamber being arranged at the upper cover; a gas inlet mechanism, the gas inlet mechanism including a first insulation block, a second insulation block, a gas inlet pipe and a flange part, one end of the gas inlet pipe being connected to the flange part, at least a part of the first insulation block being located in the through-hole, the second insulation block being provided with a second gas inlet hole, the gas inlet pipe being communicated with the second gas inlet hole, the first insulation block being provided with a first gas inlet hole, one end of the first gas inlet hole being communicated with the second gas inlet hole and another end of the first gas inlet hole being communicated with the inner chamber, a projection of the first gas inlet hole being located outside a projection of the second gas inlet hole in an axis direction of the through-hole; characterized in that a side of the first insulation block facing away from the inner chamber being provided with an accommodation space, the second insulation block being arranged in the accommodation space, the flange part being arranged at an opening of the accommodation space and being located above the second insulation block, an outer surface of the second insulation block being provided with a gas inlet groove, the gas inlet groove and an inner wall of the accommodation space forming the second gas inlet hole; a side of the second insulation block facing the inner chamber being provided with a first groove, the first groove and the inner wall of the accommodation space forming a first gas chamber, and both of the first gas inlet hole and the second gas inlet hole being communicated with the first gas chamber. a chamber body, the chamber body being grounded; an upper cover, the upper cover being provided with an electrode, the chamber body being connected to the upper cover through an insulation member, the chamber body and the upper cover forming an inner chamber, and a through-hole communicating with the inner chamber being arranged at the upper cover; a gas inlet mechanism, the gas inlet mechanism including a first insulation block, a second insulation block, a gas inlet pipe and a flange part, one end of the gas inlet pipe being connected to the flange part, at least a part of the first insulation block being located in the through-hole, the second insulation block being provided with a second gas inlet hole, the gas inlet pipe being communicated with the second gas inlet hole, the first insulation block being provided with a first gas inlet hole, one end of the first gas inlet hole being communicated with the second gas inlet hole and another end of the first gas inlet hole being communicated with the inner chamber, a projection of the first gas inlet hole being located outside a projection of the second gas inlet hole in an axis direction of the through-hole; characterized in that a side of the first insulation block facing away from the inner chamber being provided with an accommodation space, the second insulation block being arranged in the accommodation space, the flange part being arranged at an opening of the accommodation space and being located above the second insulation block, an outer surface of the second insulation block being provided with a gas inlet groove, the gas inlet groove and an inner wall of the accommodation space forming the second gas inlet hole; a side of the second insulation block facing the inner chamber being provided with a first groove, the first groove and the inner wall of the accommodation space forming a first gas chamber, and both of the first gas inlet hole and the second gas inlet hole being communicated with the first gas chamber.