Abstract: Bromothymol blue (BTB) was polymerized on the surface of GCE in a phosphate buffer solution by CV in the potential range of -0.8 to 1.6 V, with scanning for 15 cycles, to form BTB modified GCE. A portion of 10 mg of carbonylated MWCNTS was dispersed in 10 mL of DMF, and an appropriate amount of the dispersion was dropped on the surface of the BTB/GCE, forming the modified electrode of MWCNTS/BTB/GCE, which was dried under ultra-red lamp. As shown by the CV study, significant response of adenine at the MWCNTS/BTB/GCE was observed in phosphate buffer at pH 6.8 with scanning rate of 100 mV·s^-1. It was proved that the modified GCE was suitable to be used as a sensor for CV determination of adenine in Cordyceps sinensis. Linear relationship between values of oxidative peak current and mass concentration of adenine was obtained in the range of 0.05-1.0 g·L^-1, with detection limit (3s) of 0.025 g·L^-1. 5 samples taken from different batches were taken and analyzed by the proposed method, giving results in consistency with the labelled values. Values of RSDs (n=5) found were in the range of 0.8%-2.0%.