Since near 80% of the raw material for paper production in Taiwan is recycled fibers, researches on recycled fibers can directly contribute to our paper industry. The objective of this study is to investigate the feasibility of alkaline sizing with different recycled fibers and to compare the sizing results with that of virgin fibers. Additionally, this research attempts to improve the outcomes of alkaline sizing with recycled fibers by adding calcium carbonate pigment, adjusting the sizing temperature, and performing alkali treatment before the sizing procedures. Experimental results indicate that AKD is a better alkaline size than ASA and rosin size for recycled fibers. Moreover, deinking treatment is found as a prerequisite for an effective alkaline sizing with recycled fibers. Furthermore, both the presence of calcium carbonate and the practice of alkali treatment improve the handsheet's sizing results. The sizing temperature should be controlled at 40aC for optimum results, either lower or higher temperatures would not promote the sizing performance. Finally, the contact angle which is a significant variable for paper sizing analysis has been calculated and presented in this report through the technique of mathematical modeling.