Yb, Er co-doped NaYF4 (NaYF4: Yb3+, Er3+) up-conversion phosphors (UCPs) were synthesized through hexadecylpyridinium chloride and tri-sodium citrate binary cationic/anionic capping agent assisted hydrothermal reaction. The effects of doping amount of sensitizer (Yb3+) and activator (Er3+) on luminescence properties of NaYF4: Yb3+, Er3+ were systematically investigated. A series of luminescent polymer composite films were prepared by aqueous solution casting method employing poly(vinyl alcohol) (PVA) as a matrix polymer and different kind of UCPs as the filler. It was found that the fluorescent intensity of the UCPs was firstly increased and then decreased with the increasing of Yb3+ doping amount. With the doping amount of Yb3+ kept at 30%, the resultant UCPs showed the strongest fluorescent intensity. Besides, the increasing of Yb3+ doping amount from 10% to 98% led to the decrease of the green to red emission ratios and the resultant UCPs exhibited different emission colors ranging from green to yellow and then to orange. The effect of Er3+ doping amount on the fluorescent property of UCPs was also examined. The tendency was similar to that of Yb3+ doping amount effect. With the increasing of Er3+ doping amount, the fluorescent intensity of the UCPs was firstly increased and then decreased. With the doping amount of Er3+ kept at 1%, the resultant UCPs showed the strongest fluorescent intensity. The doping amount of Er3+ also affected the green to red emission ratios, which endowed the UCPs with different up-conversion emission. The transparent PVA composite films with tunable up-conversion emission may find practical application in the field of anti-counterfeiting packaging.