In the present study,the model for cotton-root water uptake with drip-irrigation under mulch film was established based on field experiment. With the model,water dynamics and redistribution was addressed under the condition of cultivation.The fundamental mechanisms of water uptake by cotton roots were carefully discussed.Core samples were collected by drilling separately in wide rows and narrow rows of cotton plants,and the root samples were then separated by water from the soil cores for measuring root lengths.Based on the root lengths,a distribution model was developed regarding root length density of cotton.Based on theoretic analysis and mathematical calculation,one-dimensional cotton root uptake model was built by incorporating factors such as root length density,soil moisture content and plant evaporation.The model had a simple structure with only a few parameters.The cotton root uptake model matched well with field observation and is readily to be applied.