Brass specimen, copper based alloy was prepared in cubic form about $1cm{ imes}1cm{ imes}1cm$ in volume. The specimens were mechanically compressed in one direction until the dimension distorted to 20%, 40%, 60% and 80% in length. The compressed specimens with 80% distorted in length were then heat treated in $200^{circ}C$, $300^{circ}C$, $400^{circ}C$, $500^{circ}C$ and $600^{circ}C$ for 30 minutes. Microscopic examination was made on both compressed and heat treated specimens. The results obtained from the study were as follows: 1. Grain boundary and twin phenomenon was clearly seen in 0% and 20% compressed cases. Slip bands was appeared in 40% cases and distributed equally as well as twin. 2. The first evidence of slip bands was observed in 20% and the bands grew thicker and denser as the compression increased. 3. The density of the bands were reduced after annealing in $200^{circ}C$ and completely disappeared at $300^{circ}C$ cases. 4. Recrystallization was noticed unevenly in $300^{circ}C$ cases and the evidence of twin was observed in these crystallized area. 5. In $400^{circ}C$ cases the grain boundary was evenly found and the twin phenomenon was clearly observed. Grain boundary and twin was noticeably formed in size according to the annealing temperature increased.