This research was about improving students’ vocabulary through
Demonstration Technique. The objective of this research was to improve students’
vocabulary mastery of the tenth grade students in one of senior high school in
Purwokerto using Demonstration Technique. The participants of this research were 34
students of tenth grade in one of senior high schools. This research was conducted in
two cycles. Each cycle consisted of planning, acting, observing, evaluating, and
reflecting. In collecting data, vocabulary test as the quantitative also observation and
questionnaire as qualitative data were used. To support the qualitative data, interview
to the students was conducted to know the students’ vocabulary problems. The results
of the research could be seen from the students observation that in cycle 1 at 76.46%
which belonged to enough criteria and in cycle 2 at 84.55% which belonged to good
criteria; the score average in post-test 1 was 71.73% and in cycle2 was 80.70%.
Students’ vocabulary test result, the score average reached ≥ 70 as the KKM, the
learning completeness reached ≥ 85% as the classical learning target. Further, from
the questionnaire, 89.11% students gave positive response to the implementation of
Demonstration Technique during the learning process. Moreover, from the interview,
most of the students also gave positive answer of the questions given. Based on the
result of the research it could be concluded that the use of Demonstration Technique
could improve students’ vocabulary mastery.