By using chip-by-chip, mainly separation technology, micro LED can be made very accurately and efficiently. First, after epitaxial process, the LED epi-wafer is processed into micro LEDs. Second, bonding substrates with driving circuits are provided for the LED epi-wafer. Then, each LED chip is fastened to the substrate chip-by-chip simultaneously or sequentially, and each LED chip may be transferred by using separation technology simultaneously or sequentially. The LED epi-wafer per se can be also provided as LED display substrate.