A novel method is developed for the determination of cefradine by using sodium nitroprusside as chromogenic reagent. The experiment indicates that a russety product is formed by the reaction of cefradine with sodium nin'oprusside in basic solution, and the maximum absorption wavelength (λmax) of russety product is 505 nm. And the sensitization of tetradecyl benzyl dimethyl ammonium chloride for the reaction of cefradine with sodium nitroprusside is remarkable. The apparent molar absorption coefficient (ε505)is 2.81 x 103 L/mol cm. The linear equation is A = 0.0657 + 0.00804C (μg/mL) in the range of 1.50-55.0 μg/mL of cefradine with a correlation coefficient r = 0.9992, and the detection limit is 1.38 μg/mL. This method has been applied to determine cefradine in capsule and tablet samples.