Compared with the peripheral A/D conversion device with one built inside the Single\|chip,computer is much more simple and convenient for use.And it is easy to get high signal to noise ratio.But the resolution is always not high enough to satisfy the requirement for precision measurement.A practical effective method for enhancing the resolution of A/D conversion device built inside the single\|chip computer is proposed in this paper,which can increase the orignal resolution by 1~3 times only with simple peripheral circuit and internal software calculation.