In order to more effectively protect the security of network information, confidentiality and authentication of message need to be realized at the same time. Signcryption performs signature and encryption simultaneously in one logical step. In order to improve safety and efficiency of existing signcryption, an identity-based aggregate signcryption scheme was proposed by combining the ideas of aggregate signature. Under the random oracle model, the scheme was proved to be indistinguishable against adaptive chosen ciphertext attacks, and existentially unforgeable against adaptive chosen messages attacks. The security could be reduced to the elliptic curve discrete logarithm problem and computational bilinear paring Diffe-Hellman problem. Compared with serveral schemes with high efficiency and short key length, the analysis of results shows that the new scheme's signcryption and unsigncryption has only one pairing operation, thus has the excellent features with low computational cost and short length of ciphertext.