In this book, we are interested in studying and modeling an octo-copter. Knowing the weight, we have chosen the multi-copter which is an octo-copter, as well as the necessary components. Then, considering the important interest of the thrust in the construction of the octo-copter, we have designed a test bench able to measure this force basing on a propeller mounted on a brushless motor. Also, we have made a simulation using CFD code. Initially, based on the comparison with anterior results, we have found the optimal model. Then, we have applied this model to our type of propeller and we have validated it with our experiments. In the last part, we have varied the length of the arm of the octo-copter to found the optimal length via the aerodynamic simulation and to propose a new design of the whole frame.