A household microwave oven can be modified not only to be able to regulate microwave power continuously (including the intensity of EM field in the cavity),but also to be able to fit three flasks into the cavity (each flask can be connected to a reflux condenser outside the cavity).The microwave heating uniformity of the three flasks was tested using water (50g. and 30g.) and ethanol (40g.) respectively.The results showed that the heating uniformity of the three flasks was 89±5% (average±σ n-1 ,n=22) and the microwave leakage was below 1 mW/cm 2.The modified oven was used by 90 undergraduate students for chemical synthesis experiment (microwave synthesis of veratraldehyde). The reaction time was only 2～3min.and the average yield was 86±9% (n=90).The variation of the average yields of among student groups was only 2%.Through variance analysis,F1,showing the difference was not significant.This modified microwave oven is especially suitable for chemical synthesis experiment for undergraduate students and for microwave digestion in analysis labs. A household microwave oven can be modified not only to be able to regulate microwave power continuously (including the intensity of EM field in the cavity), but also to be able to fit three flasks into the cavity (each flask can be connected to a cavity the microwave heating uniformity of the three flaksks was tested using water (50g. and 30g.) and ethanol (40g.) respectively.The results showed that the heating uniformity of the three flasks was 89 ± 5% ( the modified oven was used by 90 undergraduate students for chemical synthesis experiment (microwave synthesis of veratraldehyde). The reaction time was only 2 ~ 3min. And the average yield was 86 ± 9% (n = 90). The variation of the average yields of among students groups was only 2%. Through variance analysis, F1, showing the difference was not significant. This modified microwave oven is especially suitable for chemical synthesis experiment for undergraduate students and for microwave digestion in analysis labs.