Under the conditions of constant temperature and pressure,different influences of samples with different chemical components on the mechanism of nonlinear chemical reaction will cause different changes of the potential-time relationship curve of the nonlinear chemical reaction system.Using it as the character,and using the B-Z nonlinear chemical system to use acetone and substrates in samples as main dissipative substances qua an example,the principle of nonlinear chemical fingerprint has been researched and discussed in detail.At the same time,the general method for calculating the system similarity about nonlinear chemical fingerprint was also put forward,and similarities of nonlinear chemistry fingerprints of different batches of Guhan Yangshengjing and 18 sorts of other samples were calculated by Euclidean distance,correlation coefficient,included angle cosine and system similarity,at the same time,the various similarities were analyzed.The results showed that,both of correlation coefficient and included angle cosine are unable to be used as the criterion for quantitatively evaluating the similarity of nonlinear chemistry fingerprint;as non-parametric similarity,Euclidean distance can accurately reflect the feature differences in the fingerprints,but as parametric similarity,sometimes,Euclidean distance can not accurately reflect the relative extent of characteristic difference in the nonlinear chemical fingerprints;system similarity can most truthfully reflect the characteristic difference in the nonlinear chemical fingerprints,and is the best evaluating method among the four ones.Therefore,system similarity can be used to quantitatively calculate the similar extent between the nonlinear chemical fingerprints.An economical,simple and convenient,easy pushing and effective method for identifying and evaluating complicated samples has successfully been put forward. Under the conditions of constant temperature and pressure, different influences of samples with different chemical components on the mechanism of nonlinear chemical reaction will cause different changes of the potential-time relationship curve of the nonlinear chemical reaction system. Use it as the character, and using the BZ nonlinear chemical system to use acetone and substrates in samples as main dissipative substances qua an example, the principle of nonlinear chemical fingerprint has been researched and discussed in detail. At the same time, the general method for calculating the system similarity about nonlinear chemical fingerprint was also put forward, and similarities of nonlinear chemistry fingerprints of different batches of Guhai Yangshengjing and 18 sorts of other samples were calculated by Euclidean distance, correlation coefficient, included angle cosine and system similarity, at the same time, the various similarities The results showed that, both of correlation c oefficient and included angle cosine are unable to be used as the criterion for quantitatively evaluating the similarity of nonlinear chemistry fingerprint; as non-parametric similarity, Euclidean distance can accurately reflect the feature differences in the fingerprints, but as parametric similarity, sometimes, Euclidean distance can not accurately reflect the relative extent of characteristic difference in the nonlinear chemical fingerprints; system similarity can most truthfully reflect the characteristic difference in the nonlinear chemical fingerprints, and is the best evaluating method among the four ones. Wherefore, system similarity can be used to Economically, simple and convenient, easy pushing and effective method for identifying and evaluating complicated samples has successfully been put forward.