As an important task in sentiment analysis, joint multimodal aspect sentiment analysis (JMASA) has received increasing attention in recent years. However, previous approaches either i) directly fuse multimodal data without fully exploiting the correlation between multimodal input data, or ii) equally utilize the dependencies of words in the text for sentiment analysis, ignoring the differences in the importance of different words. To address these limitations, we propose a joint multimodal sentiment analysis method based on Aspect Enhancement and Syntactic Adaptive Learning (AESAL). Specifically, we construct an aspect enhancement pre-training task to enable the model to fully learn the correlation of aspects between multimodal input data. In order to capture the differences in the importance of different words in the text, we design a syntactic adaptive learning mechanism. First, we construct different syntactic dependency graphs based on the distance between words to learn global and local information in the text. Second, we use a multi-channel adaptive graph convolutional network to maintain the uniqueness of each modality while fusing the correlations between different modalities. Experimental results on benchmark datasets show that our method outperforms state-of-the-art methods.