Abstract: The adsorbing kinetics and the factors of influencing calcium ion adsorption of both deionized BKP hard wood pulp and soft wood pulp were studied in this paper. The results showed that the adsorption capability of pulp fiber rise along with the augment of the beginning consistency of Ca2+ at a low Ca2+ consistency. The saturation adsorption capability of hard wood pulp is 0.016 0 mmol/g at the content of Ca2+ 0.471 7 mmol/L, and the soft wood pulp being 0.008 4 mmol/g at the content of Ca2+ 0.220 1mmol/L, which accords with the carboxyl content of pulps. At the conditions of pH 7.5 and 25 ℃, ce/Q and ce keep excellent linearity relationship, the R2 being respectively 0.95 and 0.99. It indicates the adsorption between pulp fiber and Ca2+ is chemistry adsorption, which accords with Langmuir isothermal equation, also belongs to single molecular adsorption. The adsorption capacity of chemical wood pulp fiber on Ca2+ rise along with pH or content of Ca2+, and the saturated adsorption content of Ca2+ of both BKP hard wood pulp and BKP soft wood pulp is 0035 6 mmol/g and 0.016 5 mmol/g, the pulp being entirety saturated adsorption with Ca2+ after pH 7. Arising temperature will low the adsorption capacity, which belongs to exothermic adsorption between pulp fibers and Ca2+.