In this paper, the Space Gravity Optimization (SGO) algorithm is presented as a new meta-heuristic optimization tool to determine Feasible Design Target Space (FDTS) for a microwave amplifier subject to the potential performance of the employed transistor. In this optimization problem, the search space is four-dimensioned consisting of the real and imaginary parts of the source and load terminations of the transistor and the position of each asteroid gives the candidate solution. Asteroids with the less cost values will have a higher amount of masses than the others. In this algorithm, the speed and acceleration of the asteroid having the maximum amount of the mass will be assumed to be equal to zero while other asteroids with lesser masses will be forced to have accelerations and speeds due to the gravity field of the heaviest asteroid. This results in change the coordinates and the costs of the asteroids. Thus, the solution space of the problem domain will be searched until the iteration reaches to its maximum value or the cost value of the heaviest asteroid is equal or less than the required cost value. In the final part of the work, the proposed SGO approach is implemented to determine. The FDTS of a selected microwave low noise transistor and the numerical results will be compared with their analytical counterparts . Furthermore performance of the SGO algorithm is compared with those of the Particle Swarm Optimization , Honey Bee Mating optimization algorithms  and advantages and disadvantages are concluded.