To solve the problem of redundant tasks in space reconnaissance demand, a method for space reconnaissance task relevant degree analysis was proposed, considering the sources of demand, requirements of quality, time preference and spatial range. The relevant elements of space reconnaissance were analyzed, and calculation method of task relevant degree was given based on these four elements. A specific algorithm to reduce probability of redundancy tasks was proposed with task relevant degree. An algorithm of redundancy analysis was considered in the case of accurate priority, justice and hybrid. An example was given to illustrate the effectiveness of this method. The results show that the method has good versatility, which can effectively support space reconnaissance missions preprocessing.