Abstract: The surface of an up-conversion luminescence material was modified with carboxyl group in the way of grafting modification. The influencing factors including reaction time, buffer solution and finishing agent's mass were investigated by experiment. This modification method has resolved the problem that when an up-conversion luminescence material is used as fluorescence labeling, it cannot covalently fix biological activity molecules directly. The experimental results show that when the reaction time is 4 h, the PB buffer solution is pH=9.0 and 0.50 mol·L^-1, agent to original materials is activity carboxyl group. the volume of adding the buffer solution is 50 mL, and the mass ratio of finishing 12, the surface of an up-conversion luminescence material is mostly modified with