In order to hold the design of the accelerometers

the model of silicon micromachined capacitive accelerometer in mechanical domain is designed

a fully-differential 2nd order sigma-delta analog-to-digital converter（ADC） for use as an interface circuit for accelerometers to sense the acceleration is researched

and the circuit to sense the little change of the capacitor is improved.The MEMS design tools ConentorWare are used to deal with the simulation about the system combined the mechanical and electronical models

and show the results.Useful reference in design of whole system

which is closer to the practice is provided.