This invention discloses an air pipe joint for inspecting a substrate, including a hollow pipe body and a light source. The pipe body comprises a first pipe body and a second pipe body which are bent to and communicated with each other. Free ends of the first pipe body and the second pipe body are respectively an air inlet end for connecting an air intake pipe and an air outlet end for discharging air. The light source is fixed inside the pipe body. The light emitted by the light source is emitted from the air outlet end. This invention further discloses a measurement system for substrate inspection. The air pipe joint can emit light from the air outlet end thereof, reduce a blind spot on the transparent stage and influence on measurement accuracy due to a blocking of the air pipe joint itself against the light source.