Abstract: In the recent years, areas of crayfish-rice culture are greatly increased in Lower-and-Middle Section of Yangtze River. This farming model has changed the structure of the field and water-use model. The determination model of irrigation quota is different from general crop and more complex. In this study, we established a method to determine irrigation quota of crayfish-rice culture. The study took Qianjiang city of Hubei Province as a case. By investigation in March 2018, we found the crayfish-rice culture in this study area was carried out in fields with crayfish ditch around the paddy field. The culture was divided into 3 stages in a year: crayfish-rice culture at growing stage of rice, crayfish-rice separate culture at growing stage of rice and non-growth stage of rice. During non-growth stage of rice, water body in the paddy field was connected with crayfish ditch. The water layer control model was established based on water balance equation during each stage to calculate irrigation quota. In addition, the quota of water change from poor to good quality was required if the irrigation water quality was poor. Thus, the total irrigation quota of crayfish-rice culture was the sum of irrigation quota at each stage and quota of water change. In 2017, the crayfish-rice culture area reached 46.7 khm2 in Qianjiang city. A case study was taken as an example of application of the calculation method in Qianjiang. The field length of crayfish-rice culture was 260 m. The width was 100 m, The width of crayfish ditch was 4 m, its depth was 1.5 m, the slope was 1:1 and the ridge height was 0.5 m. The evaportanspiration of rice was calculated based on Penman-Monteith formula with meteorological data from 3 experimental stations. The other data were from these stations. Due to good water quality, we didn't consider the water change quota. The crayfish-rice irrigation quota was calculated by the proposed determination method. According to calculation, the annual average irrigation quota of crayfish-rice culture was 12 945 m3/hm2, which was high than irrigation quota of rice. The irrigation quota of crayfish-rice culture at frequency of 50%, 75%, 85% and 90% was 13 185, 14 335, 14 925 and 15 285 m3/hm2, respectively. The irrigation quota was not greatly different among different frequency. According to Standard, the multiyear irrigation quota of rice in this study area was 4 050 m3/hm2. According to this study, the irrigation quota during growing stage of rice was 5 370 m3/hm2, which was higher than the Standard. It was because the irrigation quota in this study included the water for crayfish-rice culture. The investigation on this study showed that the irrigation quota of crayfish-rice culture was about 3 times of that of rice, about 12 150 m3/hm2. It was closer to our study (12 945 m3/hm2). It confirmed the practicability of proposed calculation model. The research provides a calculation method for irrigation quota determination of crayfish-rice culture, and have guiding significance for irrigation and water resources management.