Forestry plays an important role in ecological environment protection and sustainable economic development, and forestry diseases and insect pests are the main factors restricting forestry development. In recent years, with the development of modern technologies such as remote sensing, machine vision, biology and the internet of things, an important means has been provided for accurate, rapid and large-scale forest pest monitoring and early warning. Therefore, a comprehensive review was made on the application of modern technology in forest pest monitoring and early warning, aiming at providing technical reference and auxiliary decision basis for relevant practitioners. In terms of remote sensing, the mechanism of forest pest monitoring based on spectral response was introduced, and the latest application progress of remote sensing technology in forest pest monitoring was discussed from different scales. In the aspect of machine vision, the advantages and disadvantages of traditional machine learning and deep learning were compared, and the help of transfer learning to network training and the feasibility of lightweight model in improving monitoring efficiency were analyzed. In biology, how to use the biological characteristics of insects and biological changes in plants to monitor insect pests and diseases were analyzed. On this basis, the combined application of internet of things, 5G and other network technologies with modern monitoring technology was expounded for remoting monitoring and early warning of forest pests and diseases. Finally, in view of the current forest disease and pest monitoring was not timely, the evolution was not clear, the early warning was not accurate, the prevention and control was not accurate and other problems, it should be urgent to establish the ground and air three-dimensional pest monitoring network with the internet of things technology as the core in the future, build a complete pest and disease database, and establish a multi-terminal online real-time information display monitoring and early warning system.