Abstract: Through researches on cubic equatiion of state (CEOS) and numerical algorithm, some numerical computation methods (e.g. Newton method, linear interpolation method, quadratic interpolation method, and multiple iterative method) were used for derivation of explicit formula of CEOS. After simplification and verification of PR gas state equation, the explicat formula of PR equation of state was proposed. With no need for iteration, the simplified equation can be used not only for manual calculation, but also for calculation by spreadsheet or any programmable languages. Accordingly, the equation can effeceively reduce demands for computer programming and numerical algorithm levels of professionals in chemical or oil and gas industries. Accuracy and durations of calculation are verified using several hundreds of data sets, showing that the proposed explicitation PR equation of state involves more simplified calculation than iterative method. With relative error maintained below 10^-5, duration calculated by the proposed equation is only 1/10 of that calculated by the iterative algorithm, thus improving the simulation efficiency of natural gas pipeline.