Abstract: In this paper, the optimum of the fuel consumption in close impulse interception within a fixed period of time by principal vector theory was mainly studied. Then a mathematical model of space interception of short distance based on the theory of orbital dynamics was set up. According to the principal vector theory, a theoretic criterion was put forward to determine whether the optimum of impulse interception has been attained, and an optimization technique for the interception was raised too. The effectiveness of the optimization was verified by lots of simulation examples. In the latter part of the paper, the fuel consumptions of the space interceptions at different time were simulated, compared and analyzed, and at last a technique to achieve optimal fuel consumption of the interception was brought forward.