In this paper, a hybrid integrated micro fiber spectrometer is put forward. A holographic concave grating is adopted as dispersing and imaging element, which can easily realize the flat spectrum plane. The detecting element is linear CMOS image sensor. The spectrum range of this micro spectrometer is from 400 nm to 800 nm. The whole system has many advantages, such as a few optic elements, higher transfer efficiency, compact structure and small volume. The structure and parameter of this micro spectrometer are optimized. First xxperiment and computer simulation are carried out to test the design. The results has been showen that this micro fiber spectrometer has a good performance.