A novel simulation technique for the flow in plastic mixers based on Element-free Galerkin Method (EFGM) has been developed in this study. To improve the simulation accuracy, a "rearrangement" scheme has been employed which eliminates errors caused by the irregular distribution of data points. Through several numerical tests, the new simulation technique has been validated to be applicable to high viscosity fluid flow with enough accuracy. Furthermore, simulation examples for realistic mixers were carried out using the developed technique. From the results, it was found that the developed technique is capable to investigate the relationship between flow behavior inside realistic mixers and operating conditions.