A new type of nuclear density gauge controlled by micro-computer was presented. A series of new techniques

such as non-linear fitting of density

automatic compensations for the deviations due to the decay of the radioactive source and the medium′s temperature

etc.

were employed. Comparing with old types

this gauge has such advantages as high precision

simple operation and automatic calibration. It can be widely used in on-line density measurement various fluids passing through pipe lines.