Cloud manufacturing is one of the three key technologies that enable intelligent manufacturing. This paper presents a novel attribute-based encryption (ABE) approach for computer-aided design (CAD) assembly models to effectively support hierarchical access control, integrity verification, and deformation protection for co-design scenarios in cloud manufacturing. An assembly hierarchy access tree (AHAT) is designed as the hierarchical access structure. Attribute-related ciphertext elements, which are contained in an assembly ciphertext (ACT) file, are adapted for content keys decryption instead of CAD component files. We modify the original Merkle tree (MT) and reconstruct an assembly MT. The proposed ABE framework has the ability to combine the deformation protection method with a content privacy of CAD models. The proposed encryption scheme is demonstrated to be secure under the standard assumption. Experimental simulation on typical CAD assembly models demonstrates that the proposed approach is feasible in applications.