Abstract: Based on the principle of the Nessler′s colorimetric determination of NH+4 ion,a new instrument,named “Rapid Determinator for Meat-freshness” was designed and fabricated.By using this self-made determinator,freshness of a meat sample was determined within 8 min.Linear relationship was obtained between the absorbance and concentration of NH+4 in the range of 0-40 mg per 100 g of sample,with its correlation coefficient over 0.995 and detection limit of 2.5 mg per 100 g (3S/N).The average value of RSD′s (n=8) found in the analysis of 2 samples with different concentrations of NH+4 was 3.5%.