The present invention proposes a relaxation state evaluation system and method and a computer program product thereof. The method comprises steps: measuring ECG data of a user; analyzing the ECG data to generate a first, second, third and fourth parameters, wherein the first parameter is the short-scale entropy slope of the user before cardiovascular disease treatment (CVDT); the second parameter is the difference of the post-CVDT and pre-CVDT mean RR intervals; the third parameter is the logarithm of the variance of the pre-CVDT high frequency NN intervals; the fourth parameter is the logarithm of the ratio of the variances of the pre-CVDT low frequency and high frequency NN intervals; working out an evaluation index, which is a function of the abovementioned parameters; and evaluating the relaxation state of the user, wherein the user is determined to be in a relaxation state if the evaluation index is over a threshold.