Taking common food-grade plastics such as low density polyethylene(PE-LD),polypropylene(PP),polystyrene(PS) and polycarbonate(PC) as research objects,a twin-screw extruder was used to process them many times for simulating the processing history of their reclaimed plastics,then the feasibility of ATR-FTIR,MFR,GPC,TGA and tensile strength tests for discriminating the reclaimed plastics with different processing history were investigated. The results show that ATR-FTIR can be used for discriminating PE-LD reclaimed plastic preliminarily because a new methyl characteristic peak appears in ATR-FTIR spectrogram of PE-LD reclaimed plastic processed 6 times,but the methyl characteristic peak of PE-LD reclaimed plastic processed one time is not obvious,so the ATR-FTIR method has certain limitations. The molecular weight or polydispersity index of PS and PC only decrease or increase obviously after processing them many times,so the GPC method is only used for discriminating PS and PC reclaimed plastics which are processed many times in the past. The TG curve of PC reclaimed plastic is different with that of its new plastic,but the curves of the other three reclaimed plastics are not different with those of their new plastics,so the TGA method is only used for discriminating reclaimed PC plastic. With processing times increasing,the MFR of PE-LD decreases and its tensile strength increases gradually,the MFR of PP,PS and PC increases gradually and their tensile strength decreases,which indicate that the MFR and tensile strength method all can be used for discriminating the four common food-grade reclaimed plastics.%以低密度聚乙烯(PE-LD)，聚丙烯(PP)，聚苯乙烯(PS)及聚碳酸酯(PC)等常用食品级塑料为研究对象，采用双螺杆挤出机对其进行多次挤出加工，以模拟食品级塑料再生料所经历的加工历史，然后考察了衰减全反射傅立叶变换红外光谱(ATR-FTIR)分析、熔体流动速率(MFR)测试、凝胶渗透色谱(GPC)分析、热重(TG)分析以及拉伸强度测试在鉴别具有不同加工历史的食品级塑料再生料方面的可行性。结果表明，ATR-FTIR法可初步用于鉴别PE-LD再生料，其经6次加工后的再生料会出现新的甲基特征峰，但经1次加工后的再生料甲基特征峰并不明显，故ATR-FTIR法存在一定局限性；PS及PC只有在经多次加工后其分子量或多分散性指数才有明显下降或上升，故GPC法仅能用于鉴别具有多次加工历史的PS及PC再生料；PC再生料的TG曲线相对新料有所不同，但其它3种食品级塑料再生料的TG曲线与新料相差不大，故TG法仅能对PC再生料进行鉴别；随加工次数的增加，PE-LD的MFR逐渐降低、拉伸强度逐渐升高，而PP，PS和PC的MFR逐渐升高，拉伸强度有所下降，故MFR和拉伸强度测试均可用于这4种常用食品级塑料再生料的鉴别。
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