An identification of a person is considered as a vital part of forensic work. An identification or evidence to prove a person is very important in everyday life. The substantial evidence that is used to indicate a person is “Bones”. The bone part that can be used in forensic science is the mastoid bone (Master Process). The different characteristics of different bones is an advantage to identify gender. The mastoid bone is a small bone on the identify easily. 30 Dry skulls were collected as samples for this study and separated as male 16 Dry skulls and 14 Dry skulls were females, between the ages of 20-80 years. And have been used for mathematical analysis to calculate the area under triangle with the mathematical formula. And then use the results to compare the difference of the variables in the mastoid bone (Mastoid Process) left and right, between male and female in each variable. We found the difference was statistically significant between both sides of mastoid bones. And the average area of the mastoid bone of male was larger than females. The female was at the male was at the size of 1,206.01 mm² and the male was 1,435.39 mm²