Molecular dynamics simulation was used to study the microstructure and mechanical properties of amorphous Si3N4 with a density of 2.4, 2.8 and 3.1 g/cm3, at a temperature of 300, 500, 700 and 900 K. The microstructure of the samples was analyzed using the partial radial distribution function, coordination number, bond angles and void distributions. The results show that a temperature in the range of 300 to 900 K has little effect on the microstructure of amorphous Si3N4. With an increase in sample density, there is a decrease in the effect of temperature on the microstructure. The mechanical properties were calculated looking at the uniaxial deformation of the samples. The elastic modulus E was determined from the stress - strain curve. The results also show that a temperature in the range of 300 to 900 K has little effect on the mechanical properties of amorphous Si3N4, and the effect of temperature on the mechanical properties decreases as the density of the sample increases.