Zero-gravity surface figure testing is important for space optical elements. We propose the three orientations method (TOM) to achieve this goal. The optical element is rotated according to the proposed degree of freedom, and we calculate its zero-gravity surface figure by any three rotation angles (θ₁, θ₂, and θ₃) and their corresponding surface figures (S₁,  S₂, and   S₃). The algorithm of TOM can also be applied to the face-up/face-down test and horizontal rotation test. Theoretically, TOM can get an absolute zero-gravity surface figure; however, a rotation angle error can result in a zero-gravity surface figure error. The surface figure model (SFM) and gravity-included angle model (GAM) are proposed to analyze the relationship between the rotation angle error and zero-gravity surface figure error. For numerical results, SFM is equivalent to GAM. In addition, GAM addresses the zero-gravity surface figure error, which is induced by the rotation angle error, also being regarded as a surface figure, which is caused by a certain amount of gravity. For all models, we provide both theoretical derivations and numerical examples.