In order to make full use of old newspapers and preserve precious plant resource, old newspapers were reclaimed and refined into fiber, then phthalic anhydride (PA) was utilized to modify the reclaimed-fiber on the condition of ultrasonic radiation. Subsequently, reclaimed-fiber was mixed with polylactic acids (PLA) to obtain composites by means of extrusion molding. At last, mechanical performances of the composite were tested. Results reveal that: composite made form PLA and the PA treated reclaimed-fiber from old newspapers has good mechanical performances, and its tensile strength is higher than 41.5MPa while impact strength is no less than 7.3KJ/m2. Moreover, the optimum processing conditions for modifying reclaimed-fiber with PA are: mass fraction of phthalic anhydride to old newspaper reclaimed fiber 5%, ultrasonic radiation time 15min, and modification temperature 90°C.