Abstract: Abstract: Precise feeding technology not only provides adequate nutrients for gestating sows, but also saves manpower and reduces feed wastage for breeding farms. In China, due to the expensive imported feeding equipment, most of the small and medium-scale farms with breeding swine rely on a manual feeding mode which makes it difficult to achieve precise feeding of sows. Therefore, the purpose of this paper was to develop an electronic sow automatic feeding (ESAF) system, ultimately achieving independent feeding and residual feed control for individual pregnant sows. In the system of ESAF, individual pregnant sows were identified and the information of the pregnant sows was exchanged automatically by the technologies of low frequency (134.2 KHz) RFID and a wireless local network. Since the electric door could easily result in an error due to power failure, the system of ESAF used a whole mechanical passageway to control the entry and exit of the individual pregnant sow. The whole mechanical passageway and the mechanical automatic interlock was composed of the device of a pre-passageway for the opening , the door of the passageway, the device of a pullback spring, the driving device of the pre-passageway, the fixed hurdle of the pre-passageway, the feeding controller, the device of the post-passageway for exiting, and the interlock trolley line. For example, when a pregnant sow entered into the mechanical passageway, the first nut on the top of the access door was fixed. This pregnant sow couldn't go back, and other sows could not enter. When this sow left, the first nut on the top of the front doors was lifted, and automatically shut down after another pregnant sow entered. The whole mechanical passageway and the mechanical automatic interlock were to strictly ensure that only an individual sow entered into the automatic feeder, achieving accurate identification and feeding. The feeding controller was composed of accept and transmit antenna, a display LED screen, the main control panel, the outer shell, and the cable pipes. The feeding controller which was equipped with a module of embedded chips (ARM LPC1766) could collaborate to work with the feeding electric motor and the proximity sensor, finally realizing the forward control of accurate feeding and minimum residual rationing according to a pre-set value with the cooperation of the feeder. The results of an actual test on the ESAF system showed that there were no significant effects on the number of pregnant sows' daily intake with different breeding farms and days (p>0.5). The daily feeding amount could be divided into two feedings, and the residual proportion of the feed was limited to about 2.1% no matter how strong the environment stress and body stress were. This meant that the control of the residual ration had reached the practical acceptable level. Further tests showed that, based on actual feeding twice a day, the feed intake between sows at the different stages of pregnancy were significant (p<0.05), but the actual feed intake of sows at the different stages of pregnancy were basically consistent with the default values. Therefore, it was necessary for sows at the different stage of pregnancy to be provided with a continuously incremented amount of feedstuff. In summary, the ESAF system was simple for operation, easy for maintenance, achieved high visualization, had strong adaptability, and was low cost. Therefore, it was suitable for the small and medium-scale farms with breeding swine in China.