Microwave photonics can overcome a series of bottlenecks of traditional technology such as low operating frequency, low bandwidth, high transmission loss and low ability of antielectromagnetic interference by using photonic technology to generate, transfer process and control microwave and millimeter wave signals. Lasers, electrooptic modulators and photodetectors are the three key devices of microwave photonics, thus their performance affects a lot on such indexes as noise and dynamic range of microwave photonic links. However, large size and high weight of microwave photonic system based on discrete devices limit its array applications in radar and electronic warfare. Siliconbased hybrid integrated technique and highdensity and lowloss film onchip optical transmission interconnection technique are the key technologies for solving the integration of active and passive devices. In this paper, the current developments of Sibased lasers, electrooptic modulators, photodetectors and waveguides are reviewed, and the development trends of integrated microwave photonics are discussed.