Different dimensions of fused deposition parts cause the differences in dimensional accuracy，which will mislead the optimizing process of parameters by employing different quality assessment indexes． Therefore，three types of samples with different dimensions were tested by the Taguchi orthogonal experiment method，which took layer thickness，filling velocity，nozzle temperature and filling rate as the factors and took dimensional error，dimensional deviation and build time as quality assessment indexes to investigate the influence of different part dimen-sions and assessment indexes on the optimization of fused deposition modeling process parameters． The results show that three types of samples exhibit differences in size accuracy during deposition; curves of both equivalent and each dimensional deviation values of different groups generally present an increasing trend of waves，and the fluctuation range of equivalent dimensional deviation values declines with the increase of the size of samples． Two accuracy assessment indexes are different． The dimensional deviation index are more scientifically reasonable in general，and sequences of factors for evaluating printing efficiency of these samples were the same． Finally，the results of factors＇optimized levels were compared，and the optimization scheme of the combination of process parameters of three samples under different quality requirements was proposed．