Abstract: The far-field of antenna is very important for studying the radiation characteristics of antenna, and the near-field measurement techniques which can obtain far-field by near-field to far-field transformation are widely applied because the techniques can avoid direct measurement of far-field, however, it is also very important to exam the accuracy of the far-field. To solve this problem, the spherical near-field measurement is taken as an example in this paper, in which we propose a method that mainly discusses spherical wave mode expansion theory which is key to implementing the spherical near-field to far-field transformation. The theory can develop the field in the space which is built by the antenna expanding into the sum of spherical wave functions. The weighting coefficient of the antenna includes both the information of far-field and near-field. Therefore, not only the far-field radiation characteristics can be obtained from near-field measurement information, but also the electric field of near-field can be obtained from far-field measurement information, as a result, which can test the accuracy of far-filed obtained by near-far to far-field transformation. The formula of near-field to far-field transformation is deduced, and then the far-field to near-field transformation formula is further deduced. The simulated result using the FEKO simulation software and calculated result obtained by the proposed algorithms are presented, and show very good agreement, which confirms the validation and efficiency of the algorithms.