Abstract: In order to analyze the flow pattern and the critical Reynolds number of flow pattern conversion to each other in the runner of the labyrinth emitter, the tests of the water flow for the model with five different sizes of runner were conducted, the phenomena of water flow were observed and analyzed, the relationship between the head loss and average velocity in the labyrinth runner was analyzed, and the relationship between friction loss and average velocity along the straight runner that with the same section size as the labyrinth runner was analyzed. The results show that: The labyrinth path has great disturbance on the flow, making the laminar flow change into the transition region when Reynolds number is 41.5; the laminar flow may occur in the labyrinth units at the entrance section which accounts for 10%-12% of the whole labyrinth units. as a whole, the flow pattern can be regarded as turbulence or transition region; unlike the classical Reynolds test, the head loss in the labyrinth path is proportional to the 2.0-2.5th power of average velocity of section; the flow pattern index of labyrinth emitter can be 0.4-0.5; and the critical Reynolds number of flow state conversion between transition region and the turbulence ranges from 87.5 to 125.0 in the test.