Abstract: The industrial agglomeration is an important boosting power for agricultural growth. Taking hog industry in China as the research object, and based on the relevant statistics data of 31 provinces in China from 2003 to 2017, this paper thoroughly investigated the existence and form, the regional difference, and the spatial spillover of the hog industrial agglomeration growth effect in China by different estimation methods, including the fixed effect estimation, the two stage least square estimation, the threshold estimation, the space Durbin estimation, and the maximum likelihood estimation. Results demonstrate that: hog industrial agglomeration in China shows an obvious gradient and contiguous feature. The constrained development region shows the highest industrial agglomeration, and the moderately development region shows the lowest industrial agglomeration. The industrial agglomerations also present heterogeneity among different provinces. China’s hog industrial agglomeration has a significant “inverted U” curve influence on the hog industry output. When the industrial agglomeration is low, raising agglomeration will promote hog production efficiency. When the industrial agglomeration is too high, raising agglomeration will weaken hog production efficiency. The growth effect of hog industrial agglomeration has significant double thresholds. When the industrial agglomeration is between 0.389 and 0.462, the growth effect is the strongest. The growth effect of hog industrial agglomeration has obvious regional difference. China’s hog industrial agglomeration shows significant “inverted U” curve growth effect in the potential growth region and the moderately development region, and has non-significant growth effect in the key development region and the constrained development region. The growth effect of hog industrial agglomeration also has obvious spatial spillover effects, which shows an “inverted U” curve and intensifies the growth effect. Consequently, China should promote hog industrial agglomeration in the advantage regions, enhance the growth effect of hog industrial agglomeration, and strengthen the spatial spillover growth effect of the industrial agglomeration.