Introduction: Zinc phosphate cement is one of the materials in dentistry that is used as a luting cement. Unfortunate-ly, high acidity value of zinc phosphate cement in the early application potentially irritate the pulp. The challenge to accelerate the increasing of zinc phosphate cement pH is by changing the particles of zinc phosphate cement from micro scale into nanoscale. The purpose of this study is to determine the difference in acidity value between con-ventional zinc phosphate cement and nano zinc phosphate cement. Methods: This research was an experimental re-search using posttest only control group design to see the acidity value differences of the two kinds of zinc phosphate cement. It consisted of six samples; three samples were conventional zinc phosphate cement and three samples were nano zinc phosphate cement. Each sample was measured based on eight intervals i.e 2, 5, 10, 15, 20, 30, 60, 1440 minutes after manipulating. Thus totally consists of 16 groups. Acidity value was measured by pH meter. Results: The test results showed statistically significant difference of acidity value between conventional zinc phosphate cement and nano zinc phosphate cement (p = 0.000). Conclusion: The conclusion of this research was that the acidity value of conventional zinc phosphate cement was higher than nano zinc phosphate cement.