The invention discloses a channel water distribution method and belongs to the field of irrigation. The channel water distribution method includes: establishing an encoder matrix P; calculating water distribution ending time of jth lower channel according to water distribution starting time tjx of the jth lower channel, water distribution ratio ajx, default design water distribution flow qj and actual water distribution amount Wj of the default jth lower channel which are included in the xth column of the encoder matrix P; determining value of switching variable xij in the ith time period of the jth lower channel according to the water distribution starting time tjx and water distribution ending time tjxy of the jth lower channel; calculating fit of the xth column according to flow rate ratio, water distribution starting time, water distribution ending time and switching variable of each lower channel; selecting the cth with the maximum fit from the encoder matrix P, and controlling starting and stopping and lockage flow of a gate corresponding to the jth lower channel within the water distribution starting time tjc to the water distribution ending time tjcy according to the flow rate ratio ajc. With the method, water distribution time and water distribution flow of the channel can be optimized.