In order to predict the behavior of polyimides and to optimize their fabrication, it is important to understand the relationship between polyimide's structure and their surface properties. The surface properties (water sorption and repellency, adhesion) are closely related to the surface tension of polymer solid. Critical surface tension gamma(C) and surface tension gamma(S) of a polymer solid have generally been estimated by the contact angle method. BPDA (3,3',4,4'-biphenyltetracarboxylic dianhydride)-BAPE (1,2-di(4-aminophenoxy) ethane) polyimide was successfully synthesized. Testing liquids, e.g., dispersion, polar, hydrogen bonding liquids were used to measure the contact angle 0 whose values were determined by a quantitative imaging system. Unlikely the existed contact angle measurements, our lab-made quantitative imaging system could provide accurate and reproducible values of the contact angles. The critical surface tensions gamma(C) were analyzed by a Zisman plot, a Young-Dupre-Good-Girifalco plot, and a log(1 + cos theta) vs log gamma(L) plot. The surface tension gamma(S) of BPDA-BAPE polyimide was calculated using the geometric mean equation and multiple regression analysis. The Zisman plot is essentially a downwardly convex curve with polar and hydrogen bonding liquids having gamma(C) << gamma(L). The calculated values of gamma(S)(d) (a dispersion component), gamma(S)(p) (a polar component), gamma(S)(h) (a hydrogen bonding component), and gamma(S) are 29.69, 13.17, 0.25, and 43.11 mN(.)m(-1), respectively. The gamma(S) of BPDA-BAPE polyimide is 43.11 mN(.)m(-1) which is 1.05 and 1.14 times higher than those of Kapton (R) H films, respectively. The polarity of BPDA-BAPE polyimide is 0.311 whose value was located between 0.87 and 1.39 magnitudes of Kapton (R) H films' polarity, respectively.