Gravitational wave detection is now more than a mere verification of Einstein's relativity. It opens a brand-new window to explore gravitational wave astronomy, therefore attracts increasing attention of scientists from all over the world. Focusing on space laser interferometer gravitational wave detection, we give a comprehensive review on its scientific objectives, recent status and key technologies. With arm-length being of million kilometers, a space detector works within a frequency band from 0.1mHz to 10Hz. Its possible sources include compact binary star system, extreme mass ratio inspiral, intermediate mass ratio inspiral, super mass black hole merge, etc. The success of space gravitational wave detection mission requires a pico-meter precision laser interferometer, and a state-of-the-art drag-free control system. Taking European space gravitational wave detector as an example, we analyze space laser interferometer and drag-free control system in detail. The trend and perspective of Chinese space gravitational wave detection mission are also discussed.