The reduced interest of students in learning mathematics and consider mathematics to be a difficult subject to become a serious problem in Indonesia, especially in one of the provinces in Indonesia, namely in Lampung. The purpose of this study was to determine the effectiveness of the demonstration method assisted by Multiplication Board props to the understanding of the third grade mathematical concept of Bandar Lampung. This type of research is quantitative research with the type of Quasy Experimental Design. The design used is the Pretest-Postest Control Group Design. The population of this study was class III Bandar Lampung students. The sample in this study is class III A as the experimental class with the demonstration method, class III B as the control class using conventional methods. Data analysis techniques used the normality test with Lilifors test and homogeneity test with Bartlett test. Followed by testing the hypothesis that is using independent tests. Based on the results of the analysis and discussion of the research data obtained the results of hypothesis testing manually with t[subscript count] = 4.265 and t (0.025; 38) = 1.960, so that t[subscript count]> t (0.025; 38) then HO is rejected. Based on these results, there is an understanding of the concept of mathematical multiplication between students who are taught using the demonstration method compared to using conventional methods.