Traditional spectrometers commonly suffer disadvantages of bulky size, low resolution, narrow spectral range, vibration sensibility and high price. In order to overcome the limitations of traditional devices, a novel micro-spectrometer based on optical scattering theory is proposed and demonstrated by using finite difference time domain (FDTD) simulations. The design contains a series of bubbles with different sizes, which are used to scatter the incident beams. As lights with different wavelengths have different scattering intensity anglar distributions, the pixels after the bubbles can obtain different data which can be substituted into a linear system. The reconstructed spectrum can be obtained by solving the linear system with the Tikhonov regularization method. Simulation results show that the reconstructed spectrum and the incident spectrum are basically coincident. The spectrometer can at least realize a very wide measurement range of 300～1100 nm. Furthermore, the spectrometer can be anticipated to reconstruct the input spectrum with minimum resolutions at picometer order.