Abstract: We have investigated the kinetic parameters of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and determine CO₂/O₂ specificity factor (Ω).Initial activities of rude enzyme of Rubisco in various temperature,various pH, and total enzyme activities at 25℃ were assayed among the Rubisco mutants 69-12Q⁺,68-4PP⁺ and wild type 2137⁺ in Chlamydomonas reinhardtii.The rude enzyme's optimum temperature,optimum pH and percentage of activation were determined.Analyses of CO₂/O₂ specificity factor Ω of purified Rubisco were conducted with Kostov and McFadden's graphical method.The Ω values for 69-12Q⁺,68-4PP⁺ and 2137⁺ are 13,54,and 61 respectively.Our results indicated that subtle perturbation of Rubisco subunit may exert signification effects on its catalytic properties and the Ω value can be altered by the manipulation of Rubisco molecular.Graphical determination of the CO₂/O₂ specificity factor is superior in simplicity, celerity and accuracy to traditional methods.