The invention discloses a method for optimizing an SAR antenna directional diagram test. The method includes the steps of establishing an active phased array antenna directional diagram calculating mathematics model according to the electromagnetic field theory, obtaining and calculating basic data of an active phased array antenna, calculating and storing all wave position antenna amplitude phase weight coefficients of the SAR antenna according to the design requirement and engineering realizability, and using a near-field test method to obtain antenna sub-array directional diagrams at different positions of an antenna array plane under a planar near-field test system environment. The test time of an SAR antenna directional diagram test is greatly shortened, the satellite development progress is ensured and accelerated and a reference is provided for test SAR antenna directional diagram of subsequent radar satellite models.