This paper advances a kind of micro spectrometer, which is based upon Fabry-Perot antrum's character of filtering the waves. The basic structure of the micro spectrometer is the array of
Fabry-Perot antrum which contains many different length of antrum on the substrate of silicon, consequently we can achieve the detector for several wavelengths simultaneously. The unit of probing
is a Fabry-Perot antrum, which is made up of the substrate of silicon--metal film--silicon dioxide layer-- metal film. We carried out the corresponding simulation. In the basic structure of aluminum film(14nm)- silicon dioxide layer - silver film(39nm), the resolution can reach 15nm. When the area of a unit of probing is 0.14mm x 0.14mm only, it can reach the luminous flux of miniature grating spectrum instrument(the minimum volume in the order of cm),but the volume of the part of spectrum detector is only the order of mm. The design size of the micro spectrometer is in a few millimeters. Furthermore it has no movable parts and could detect several wavelengths at the same time. It is possible to fabricate such micro spectrometer through existing process methods of IC technology.