Aspects of the present disclosure are directed to methods, systems, and computer program products for using dynamic-link library based on memory size. In the method, a request for calling a first function in a Dynamic-link library (DLL) at runtime is received first. A size of a memory allocated to the DLL is then determined. Then call relationship of functions in the DLL is obtained. At last, functions related to the first function in the DLL are loaded into the memory allocated to the DLL based on the size of the memory allocated to the DLL and call relationship of functions in the DLL.