Finite element analysis model for three kinds for micro-beam machining error is established. The finite element analysis method is used to study influence of three different types of beam width error on natural frequency

mode and detecting signal of micro gyros. It is found that the processing error of driving micro-beam size not only affect natural frequency of drive mode

but also affect natural frequency of detecting mode. The machining error of the same size micro-beam on the same diagonal will cause coupling of drive mode and detecting mode and the characteristic of modal coupling is given

and the coupling degree increases with increase of the beam width error. The modal coupling can be neglected when the same side beam width is the same and only one micro beam width exists processing error. The modal coupling will cause serious interference to detecting signal of micro gyros

and the degree of interference is positively correlated with the modal coupling degree.