Abstract: In recent years, rice-crayfish co-culture has been vigorously promoted as an ecological agricultural mode. As a direct production decision-maker, farmers’ adoption intention and its influence mechanism should be clarified for the scientific promotion and sustainable development of rice-crayfish co-culture. Based on the questionnaire survey and on-the-spot interviews data of 603 farmers in five cities of Jiangsu Province, this study explored the influencing factors and their heterogeneity of farmers’ willingness to adopt the rice-crayfish co-culture mode using the theory of planned behavior and ordered logistic model. Results show that: 1) 56.88% of the farmers in the sample were willing to adopt the rice-crayfish co-culture mode, with income expectation as the key influencing factor. 2) Behavioral attitude, subjective norm, and perceived behavioral control had significant effects on farmers’ willingness to adopt the rice-crayfish co-culture mode. The order of influence was as follows: perceptual behavior control > behavior attitude > subjective norm. 3) Under different qualifications, the factors influencing farmers’ willingness to adopt the rice-crayfish co-culture mode were heterogeneous. Specifically, complete infrastructure and part-time industrialization had a stronger influence on the willingness to adopt this mode of farmers with a high expected income. The farmers who were given subsidies and less affedcted by neighborhood had a stronger willingness to adopt the rice-crayfish co-culture mode. Farmers who were less influenced by the neighborhood had higher requirements for technical training and easeness of learning. The neighborhood effect, guidance of the agricultural technology department, difficulty of technical learning, and level of education had a significant positive effect on the willingness of farmers who participated in the technical training. Distributing subsidies and improving the guidance effect from agricultural technology departments could increase farmers’ willingness to adopt this mode in areas with incomplete infrastructure. Neighborhood effect and part-time employment had a negative impact on the difficulty of technology training, while the income expectation and environmental expectation stimulated farmers to adopt the rice-crayfish co-culture mode. Based on these results, the following policy recommendations were put forward: firstly, the government should strengthen the technical training and guidance effect; second, farmland infrastructure should be improved; third, new agricultural management subjects should be fostered quickly; and finally, differentiated incentive and guidance policies should be formulated according to farmer types.