Abstract: In view of problem of low anti-capture ability of traditional key management scheme of mobile sink, namely minimum energy consumption scheme, probabilistic scheme and polynomial scheme, the paper proposed an improved key management scheme of mobile sink. The implementing principle of the scheme is as follows: all nodes share a polynomial pool F, size of polynomial loop of sensor is 1 and size of polynomial loop of mobile sink is |F|; using advantage of abundant storage resources of mobile sink to ensure exist a shared polynomial in mobile sink and any sensor nearby, then to calculate shared key through the polynomial. If regulating distributed times of each polynomial are less than orders of the polynomial, it can ensure absolute security of polynomial, so as to realize the best anti-capture ability of nodes. The experiment result showed that the scheme improves anti-capture ability and reduces energy consumption effectively of nodes comparing with probabilistic scheme.