Scheduling theory, also known as timetable theory, is a branch of operational research with significant practical value. It not only has a wide range of application backgrounds but also possesses broad development prospects. From the perspective of the theoretical development process of scheduling theory, it can be divided into two major categories: classical scheduling theory and modern scheduling theory. Classical scheduling theory serves as the theoretical foundation, with models established on a series of clear basic assumptions, including a single or homogeneous type of resource, deterministic task parameters (such as task processing time), optimization of a single objective function, and the regularity principle that the objective function is non-decreasing with the completion time of the job. Modern scheduling theory, in contrast to classical scheduling theory, is a non-classical and novel type of scheduling theory. Its core feature lies in breaking through the above basic assumptions of classical scheduling theory. By relaxing constraints on the type of processing resources, the determinism of task parameters, the singularity and regularity of the objective function, it focuses on solving practical problems that are more in line with complex real-world scenarios, such as complex resource constraints, uncertain and random task parameters, and multiple objective functions. This paper reviews the content of modern scheduling theory, introduces its research methods and significance.