[Objective] The synergistic development of the regional water-energy-food nexus (WEFN) system was studied in order to promote the sustainable utilization of regional water, energy, and food.[Methods] Based on the theory of complex adaptive systems, an evaluation index system of regional WEFN collaborative development was constructed from three aspects of water, energy, and food. A comprehensive collaborative development model was proposed based on the conditions of various elements and the interaction mechanism based on a co-evolution algorithm and gray correlation. Taking Heilongjiang Province as an example, the collaborative development degree of WEFN and the development degree and collaborative degree of its subsystems from 2009 to 2018 were calculated to evaluate the collaborative development status.[Results] ① The development degree of each subsystem was medium, and the gap was small. The collaborative degrees had a large gap, but all showed a fluctuating upward trend. Among them, the collaborative effect of water resources on energy and food, and energy on food was obvious. ② The collaborative development of WEFN was moderate, consistent with the trend of various subsystems, and remained stable after rising fluctuations. The collaborative development of the food subsystem was the highest. ③ Poor collaboration between subsystems was the reason for the low level of WEFN coordinated development. The efficient application of water and energy in agricultural production should be used as a breakthrough to promote the coordinated development of subsystems.[Conclusion] The comprehensive collaborative development model can be effectively used to evaluate the collaborative development status of regional WEFN, and is helpful for regional sustainable development decision-making.