This study aimed to clarify implement of stem education in vietnamese high school in the unit of acid-base reagent from purple cabbage. Methodology regarded experimental design. The samples included 84 students of experimental class grade 11 of 4 high schools: 02 schools in hanoi are hai ba trung high school and van lang high school; 02 schools in thai nguyen are thai nguyen high school and gang thep high school, in the term of 2017-2018. The intervention of stem topic of acid-base reagent from purple cabbage was organized for the samples. Students’ problem solving capacity in learning about the stem topic of acid-base reagent from purple cabbage will be evaluated through their performance on conducted activities. Students’ problem solving capacity score was compared between before and after impacts. The findings showed that the students’ performances on conducted activities revealed their problem-solving capacity. The findings will clarify 1) summary of students’ problem-solving capacity comparing between before and after intervention, and 2) the development level of students’ problem-solving capacity. It found that average score of problem solving capacity of experimental class before impacts = 2.47. And, average score of problem solving capacity of experimental class after impacts = 3.13. The scores of the criteria for assessing the environmental impact of the experimental class after impact are always greater than before the impact, the value of p < 0.05, The level of es effect is 0.78. The value of es indicates that the experimental results have a moderate effect. Published under licence by iop publishing ltd.