Abstract: To solve exposure of secret key in attribute-based signcryption with anonymity for both sender and receiver, key-insulation mechanism to attribute-based signcryption was untroduced. Given the formal definition and security notions, the scheme of attribute-based key-insulated signcryption was proposed, which is provably secure under the random oracle model. The improved scheme not only satisfies the requirement of bidirectional anonymity, but also achieves forward security and afterward security, consequently reduced the hazard of key exposure. Finally, confidentiality, authentication and anonymity in attribute-based key-insulated signcryption scheme were proved based on given security notions.