Abstract: The project aimed to establish real-time fluorescent quantitative PCR detecting Nt-syr1 gene in tobacco and provided a new technique for the mechanism study of potassium regulation at the molecular level. By designing two pairs of amplification primers based the mRNA sequence of Nt-syr1 in tobacco and establishing SYBR Green I reaction system of real-time fluorescent quantitative PCR, quantitative analysis was conducted to detect the changes of Nt-syr1 gene in tobacco leaves after decapitation. The technique showed that the amplification curve had flat baseline, distinct exponential area, large and stable slope, and the coefficient of variation was very little. There was a linear relationship between threshold cycle values at which samples crossed threshold and the logarithmic values of template concentration. The result indicated that the Nt-syr1 gene was strongly expressed in tobacco leaves after decapitation about 1 hour, and the expression was enhanced about 480-fold in comparison to no decapitation tobacco, but using plant growth regulators could decrease the expression caused by decapitation.