Syntactic foams are a kind of composite; consist of polymeric matrix and hollow micro-balloons. They have high strength to weight ratio if it compare to the neat matrix material. In this paper epoxy resin as matrix and ceramic micro-balloons are used and 36 kinds of syntactic foam were fabricated to investigate the effect of preparation factors such as: mixing speed, mixing time, mixing sequence and extracting bubbles by a vacuum oven on the mechanical properties. Also, two undesirable events like micro-balloon flotation in matrix and porosity are investigated as they affect the foam`s strength. The results show that the speed and sequence of mixing are not effective seriously. However the time needed for mixing would be changed for different volume percent of micro-balloons. It should be noted that as flotation and porosity increases the compression strength decreases. Using the vacuum pressure before molding may decrease the matrix porosity for above 40% micro-balloon volume fraction syntactic foams. Converse to previous, using the vacuum pressure for below 40% micro-balloon volume fraction syntactic foams would increase the floatation and decreases the compression strength.