The isotropy is one of the important performance indexes of the six-axis acceleration sensing mechanism, which determines the measurement accuracy of the sensor. In order to obtain the complete isotropy of the sensing mechanism, a new configuration synthesis method is proposed. Firstly, based on the Newton-Euler method and the inherent scale constraint relationship between the branches, the forward decoupling equation of the Stewart-type six-dimensional acceleration sensing mechanism is constructed. Secondly, the relationship between the isotropy of the sensing mechanism and the condition number of the input matrix in the forward decoupling equation is analyzed, and the mapping relationship between the branch pose and the input matrix is analyzed. Then, the configuration synthesis steps of the fully isotropic sensing mechanism are created. Finally, following this step, a ' 12-6 ' Stewart-type six-dimensional acceleration sensing mechanism is synthesized and a virtual experiment is carried out. Comparing the two cases of adding 0.100 % random disturbance and zero disturbance, the results show that the maximum reference error of six-dimensional acceleration is 0.169 %, that is, the magnification of input and output errors is only 1.69. This shows that the new configuration has excellent isotropic properties.