The utility model discloses a visible pipe for an LDV (Laser Doppler Velometer) system and a PIV (Particle Image Velocimetry) system. Two ends of a transparent visible pipe are provided with cylindrical structures fastened by flanges so that the transparent visible pipe only can bear circumferential stress of a thin-wall cylinder; the flanges at the two ends are designed into O-shaped ring end face sealing structures and an O-shaped ring is made of oil-proof rubber; end covers are connected through a special steel flange and a bolt; and the axial force of the transparent visible pipe is borne by a long bolt. The visible pipe disclosed by the utility model has the advantages that the machining is convenient and the stressing state of the transparent visible pipe can be simplified; the technical difficulties that a pipeline of the LDV system and the PIV system for a petroleum natural gas industry and a pipeline at a fluid field property research fluid testing position in equipment need visualization are solved; and a firm foundation is laid for a fluid state visualization research of a field apparatus of the petroleum natural gas industry.