This research was an experimental research to study the effect of using activity packages for develop internal locus of control of students who studying Mathematics in second year, faculty of Education, Lampang Rajabhat University in the first semester of 2011 academic year. The sample of 60 students was obtained by simple random sampling assigned into two groups consisted of 30 students and one control group of 30 students. Experimental group of 30 students was participate in eight activities. The instruments used included a scale to rate student internal locus of control and activity packages. Data were analyzed in term of mean, standard deviation and t test. It was found that the students in experimental group had higher degree of internal locus of control than the students in control group at the .05 level of significance.