The stiction and friction influencing the yield and reliability of MEMS are reviewed in this paper.The stiction, called release-related stiction, can occur within micron gaps of Si microstuctures during the etching of sacrifacial layer by HF and drying. It can also occur after packaging of the device due to over range of input signals and is called in-use stiction. It is concluded that the capillary force of water between two Si hydrophilic surfaces at separation gap of micron is the major contributor to the release-related stiction. The origin of in-use adhesion is from the chemical state of Si surface. Coating of anti-stiction films on the surface of Si microstructures and packaging of devices under dry atmosphere or vacuum are the most important methods to prevent the in MEMS devices from stiction. The preparation technology of anti-stiction films and its problems are described. Comparing with stiction, the friction is more complex. The commercially produced accelerometers and digital mirror devices are the devices with no direct contact friction. After using anti-stiction films, the stiction is fully prevented, and even the friction is apparently decreased. However, friction still exists in MEMS of direct contact moving parts. The wear resoluted from friction will decrease the reliability and lifetime of the devices. To fabricate the films with anti-stiction and wear-resitsting ability are the key research projects in high speed moving MEMS devices.