The location information of ducks in paddy field is necessary in order to adequately explore the behavioral activities of ducks in the field and the control effect on weeds. Satellite and wireless positioning systems are difficult to adapt well in rice-duck field condition, however, ultra wide band (UWB) positioning technique is a good alternative and can adapt effectively. In this study, the use of UWB positioning system to detect the movement location information of ducks in rice field was reported. The system uses DW1000 positioning chip to build the base station with detection accuracy of 10 cm. Each tagged duck position coordinates (x, y) were computed based on TDOA (time difference of arrival) location algorithm and passed through the API (application programming interface) interface. The treatment monitoring plot area was 660 m2 (11 m×60 m rectangular plot). 6 base stations were established and each station was fixed to each of the 4 vertices of the rectangle and midpoint of the long side. Ducks activities in the field under different conditions of release density (15, 20, 25 and 30) were studied. Experimental condition of each duck density was the same and location information were collected every other 2 days. Results showed that with increase of release density, the ducks became more active. Also, the state of ducks mobility in the field gradually increased as the density increased. Corresponding to the stocking density of 15, 20, 25 and 30, the proportion of total time obtained were 69.17%, 75.33%, 77.83% and 80.00%, respectively. More ducks were found to enter into each unit cell area as the release density increased. The number of entrance corresponding to the density of 15, 20, 25 and 30 were obtained as 12.05, 17.82, 23.03 and 27.73 times, respectively. Ducklings entering cells at low frequency (1-3 times per day) had the greatest probability. But, with increase in release density, the probability to enter at high frequency (7-13 times) also increased rapidly. The control effect on weeds was found to be much better when the feeding density was high. However, the purpose of duck's field activities was to get food, therefore, the larger the stocking density, the more competition for food. Accordingly, the more time ducks were in the field, and the frequency of entering into each unit cell, the more opportunities for weeding. The research results therefore will provide a reference for the further optimization of the technical process of duck rice. [ABSTRACT FROM AUTHOR]