Gelatin methacryloyl (GelMA) hydrogels have become a key biomaterial in various biomedical fields, such as tissue regeneration engineering and drug delivery, due to their exceptional biocompatibility and customizable physical and chemical characteristics. The resemblance of GelMA to the extracellular matrix and its ability to be cured with light make it a popular choice for researchers. This research delves into how the material properties of GelMA hydrogels, specifically the density of the molecular network (DMN), impact their performance in different applications. By preparing GelMA hydrogels with different degrees of substitution (DS) and concentrations, and utilizing these attributes as key measurable parameters for determining DMN, we conducted a comprehensive evaluation of properties relevant to biological applications. We also suggest strategies for optimizing these properties. Through the application of the DMN theory, we show that precise control over material properties allows for tailored customization of GelMA hydrogels for specific tissue engineering and drug delivery purposes. This study offers valuable insights into the optimization of GelMA hydrogel properties to advance the field of tissue engineering and improve customization of cellular microenvironments.