Abstract: A novel sensor was prepared using poly(diallyldimethylammonium chloride)(PDDA) and mercaptoaceti acid(MA) through the electrostatic self-assembly technique and was used for the detection of nitrite. Experimental conditions were optimized. PDDA-MA/Au responded to NaNO₂ in the linear range from 6.9×10^-7 to 8.8×10^-3 mol/L (r=0.999 8) with a detection limit of 6.9×10^-7 mol/L in 0.2 mol/L phosphate buffered saline(PBS, pH 7.53, 0.1 mol/L NaAc). The recovery ratio of the sensor was 94.6%~101.8%. Experiments showed that the sensor is of easy preparation, low cost and responses rapidly with high sensitivity and good reproducibility, stability. The sensor possesses a potential application value.