As space-based cameras have advantages of lower energy consumption, higher accuracy, and easy to be miniaturized when they are used to observe space objects with middle or smaller sizes, this paper explores the orbit determination method and observability calculation method of space objects by space-based cameras. The advantages that the sun synchronous orbit is set as a space-based satellite orbit are analyzed and a space-based satellite orbit is designed by referencing several foreign space-based satellite orbits. Then the visible arc sections of space objects for different orbit types are simulated based on the space-based satellite orbit. According to the orbit measurement accuracy of existing space based optical observation equipment and errors of orbit dynamic model, the different system errors ,random errors and dynamic model errors for the orbit measurements are added. Finally, the orbit determination precisions for space objects in different orbital altitudes are analyzed. Analysis results show that, for determining space target in low earth orbit with 6 of 7 minutes a day / two days of space-based optical measurement orbit data, the orbit determination precision is coincident with that of the United States of America cataloging (Two-line Elements,TLE) when the orbit measurement accuracy is better than 30″ and the dynamic model error is less than 50%. Moreover, for determining space target in earth synchronous orbit with 10 min / day of space-based optical measurement orbit data, the orbit determination precision is in the orbit accuracy range of the United States of America cataloging when the orbit measurement accuracy is better than 10 " and the dynamic model error is less than 50%.