The invention discloses a portable Fourier transform infrared gas analyzer suitable for a field complex environment. The analyzer comprises a light source assembly, an interface sealing ring assemblyI, a cable group I, an angle mirror type Michelson interferometer and light path assembly, a power panel, a cable group II, an electrical mainboard, an interface sealing ring assembly II, an interfacesealing ring assembly III, a gas chamber, a battery, a gas pump and an electromagnetic valve; the light source assembly comprises a collimating mirror, an infrared light source and a third plane mirror; and the angle mirror type Michelson interferometer and light path assembly comprises a light transmitting window piece, a first plane mirror, a second plane mirror, a laser detector, a beam splitter, a fourth plane mirror, a first sealing window piece, a second sealing window piece, an infrared detector, an ellipsoidal mirror, a parabolic mirror, a movable mirror, a fixed mirror and a laser device. The gas chamber comprises a third sealing window piece, a first concave mirror, a second concave mirror, a third concave mirror and a fourth sealing window piece. Technical indexes and environmental applicability of the analyzer are superior to those of corresponding foreign products, and the analyzer can be popularized and used in vast areas of China.