Abstract: The yield increasing potential of irrigation was the basis of the construction of irrigation facilities on a regional scale. In this study, the maize yield increasing potential of irrigation in Heilongjiang province was evaluated using a process-based model "Hybrid-Maize." Through two field experiments in Qixing and 850 farms in Heilongjiang, the Hybrid-Maize model was verified and showed a good simulation in both irrigation and rain-fed conditions. To study the maize yield increasing potential of irrigation (the yield gap between irrigation and rainfed yield potential) in Heilongjiang province, modeling work combined with agronomic practice (cultivar, plant density and growth durations) and historical meteorological data was conducted. Modeling results showed that the maize yield increasing potential by irrigation was highest at the first accumulated temperature zone and was low at the third, fourth and fifth accumulated temperature zones. The west representative sites of the first and second accumulated temperature zones showed higher yield increasing potential of irrigation than the east representative sites. Regional modeling results showed that, under condition of irrigation, there was the highest yield potential with more than 15 000 kg/hm2 in the southwest region of Heilongjiang province, and under condition of rain-fed, there was the highest yield potential with 14 000-14 799 kg/hm2 in the east region of Heilongjiang province. From the southwest to the east and north, the yield increasing potential of irrigation showed a declining trend from more than 1 600 kg/hm2 to less than 300 kg/hm2. When the mean growing season and annual precipitations were less than 350 mm and 430 mm respectively, the variance of the yield increasing potential of irrigation was the largest. In conclusion, we suggest that the south-west area in Heilongjiang province, where the mean growing season and annual precipitations were less than 350 mm and 430 mm in the first and second accumulated temperature zones, should be the priority area for the construction of irrigation facilities. The study can provide references for reasonable irrigation facilities construction in Heilongjiang.