Variability may be a common property of AGNs. It provides a powerful tool to study the physics of AGNs. For QSOs, variability is a suitable criterion for selecting candidates. Many variability studies on quasar samples have been made (e.g. Netzer and Sheffer 1983, User et al. 1983, Pica and Smith 1983, Wampler and Ponz 1985, Neugebauer et al. 1989, Huang et al 1990, Cristiani et al. 1990, Giallongo et al. 1991, Cimatti et al. 1994, Treverse et al. 1994, Hook et al. 1994, Cristiani et al. 1996, Axetxage et al. 1997). In some studies, a large percentage of quasars is found to have detectable variation. However, other studies find no variability evidence. Many studies also discuss the correlations of variability with luminosity or redshift. Some interesting results have been made. However, up to now, there are no positive conclusions. Further study on variability of quasar samples is obviously needed. In this paper, we report on a variability study of 32 members at the Medium Bright Quasar Sample (Mitchell et al. 1984). The study is actually a continuation of the previous study (Huang et al. 1990).