In Vietnam, using ICT in teaching and learning all subjects in secondary schools has been encouraged since many years ago; particularly for mathematics, Geometer's Sketchpad have been popular. As we knew, in the fast-growing trend of information technology, much of software appeared which was very helpful for users. Among dynamic software packages for teaching and learning mathematics, GeoGebra was one such new software; the strong point of this software is the combination of dynamic geometry, algebra, calculus and spreadsheet; therefore, it is very comfortable for teachers and students. As a lecturer of the School of Education, Can Tho University, I found it necessary to introduce GeoGebra to the teachers of provinces in Mekong Delta - Vietnam. In 2014, we have just opened a training course on how to apply GeoGebra to teaching mathematics; there were 27 secondary school teachers in Mekong Delta (Vietnam) attending. The result was that all participants began to prefer GeoGebra, also agreed that it is very handy and helpful in teaching mathematics.