In oil and gas well cementing, a strong cement sheath is wanted to insure long-term safety of the wells. Successful completion of cementing job has become more complex, as drilling is being done in highly deviated and high pressure-high temperature wells. Use of nano materials in enhanced oil recovery, drilling fluid, oil well cementing and other applications is being investigated. This study is an attempt to investigate the effect of nano materials on oil well cement properties. Two types of nano materials were investigated, which are Nano silica (>40 nm) and Nano Alumina (80 nm) and high sulfate-resistant glass G cement is used. The investigated properties of oil well cement included compressive strength, thickening time, density, free water and rheological properties. All tests are conducted according to API specification and proceed in Laboratory of Drilling in Petroleum Technology Department in University of Technology and in Missan Oil Company. The experimental results show that NS and NAL behave like accelerators when added to cement and work to increase the compressive strength at 38°C but these increasing in compressive strength changes when the temperature is increased to 60°C. Also, adding NS and NAL lead to increasing in rheological parameter and reduce free water but the change in density is very small. The results show that the effect of NAL on compressive strength and thickening time is greater than the effect of NS but the effect of NS on free water and rheology is greater than the effect of NAL.