Recent text-to-image (T2I) diffusion models have made significant strides in generating high-quality images from diverse textual prompts. Despite this progress, these models often face challenges in accurately understanding and synthesizing complex prompts, primarily due to their limited compositional capabilities. In this study, we propose a novel approach for compositional T2I synthesis using layout-guided diffusion models, which do not require additional training. Specifically, we leverage the chain-of-code prompting technique of large language models to interpret textual prompts and generate object layouts with spatial coherence. To enhance the alignment between generated images and textual descriptions, we introduce two innovative layoutguided loss functions: Patch-oriented Cross-Attention (PCA) loss and Region-oriented Cross-Attention (RCA) loss. The PCA loss emphasizes high activation values for image patches that attend to all tokens in the prompt across the layout. The RCA loss enhances the average attention within the layout, thereby increasing the accuracy of generating objects and their associated attributes within specified regions. These proposed loss functions reassign cross-attention in diffusion models during the denoising process. Our comprehensive experiments consistently demonstrate the effectiveness of our approach in improving semantic alignment between generated images and a diverse range of textual prompts, while ensuring high usability as a ready-to-use plugin. Our code is available athttps://github.com/gxl-groups/Compositional-T2I.