Aiming at the problem that signcryption scheme of the conditional public key cryptosystems cannot resist the quantum attack, a new signcryption scheme based on multivariate public key cryptosystems was proposed. Combining the central map of multilayer structure in Multi-layer Matsumoto-Imai (MMI) with the CyclicRainbow signature scheme, and using the constructure of the central map in Hidden Field Equation (HFE), the signcryption scheme was designed by introducing an improved method of constructing central map. The analysis shows that, compared with the original MMI, the scheme's key size decreases by 5% and the ciphertext reduces by 50%, and it also makes encryption and signature both realizable at the same time. In the random oracle model, its indistinguishability under the hardness of Multivariate Quadratic (MQ) problem and its unforgeability under the Isomorphism of Polynomials (IP) assumption were proved respectively. And it shows that the proposed scheme has unforgeability under the adaptive chosen-ciphertext attack as well as indistinguishability under the adaptive chosen message attack.