Agroforestry changes the traditional land use mechanism and has the advantage of intensive eco-economic compound. The photosynthetic characteristics of planting areas are the driving and restricting factors for the accumulation of plant material conversion. To investigate the response of the yield of apple-watermelon intercropping and the yield of fruit trees and crops to photosynthetic characteristics, the growth indexes, photosynthetic characteristics, yield, and benefits of single apple (CK1), single watermelon (CK2) and compound cropping modes were studied respectively. The results showed that the final growth indexes of intercropping apples were higher than those of the single model. However, due to the shading effect of high fruit trees on low crops, the normal growth of watermelon was inhibited, and the growth level of intercropping watermelon was lower than that of single mode. The Pn of apples and watermelons in different planting patterns showed a bimodal trend, and reached the peak value between 10:00–12:00 and 14:00–16:00. The daily variation curve of PAR showed an unimodal trend, and the peak value of apples and watermelons under the two planting patterns appeared between 12:00–14:00 and 10:00–12:00, respectively. Compound planting benefited apples from higher Pn and PAR, and vice versa for watermelon. The diurnal variation of Gs and Tr of intercropping and single species of apple and watermelon first increased and then decreased in an inverted V pattern, the diurnal variation trend of Ci showed a V pattern. The Gs, Tr, and Ci of apple in compound mode were higher than that of watermelon in single mode. The yield of apples increased by 46.34% in the combined apple-watermelon planting mode, and the yield of the combined planting mode was significantly higher than that of the single planting mode due to the advantage of the unit price of apples. In the apple-watermelon compound planting model, the total income was 5.19×105 yuan /hm2, the income of the single apple model was 2.46×105 yuan /hm2, and the income of the single watermelon model was 1.85×105 yuan /hm2. The land utilization rate was 232.20% and the income utilization efficiency was 210.98%.
