With the rapid development and wide application of the Internet of Things （IoT） and cloud storage technology， an increasing number of sensor devices are deployed to the Internet of Medical Things （IoMT） system every year， which promotes the popularization of Electronic Health Record （EHR）. However， the secure storage and retrieval of EHRs have not been properly resolved. To address this problem， a searchable attribute-based encryption scheme with a fixed-length trapdoor was constructed for the search and verification of ciphertext， which reduced the communication overhead required by users. By adopting the online/offline encryption technology， the computing overhead on the user side was reduced. Meanwhile， with the help of chameleon hash function， a private key with the characteristics of anti-collision and semantical security was constructed， which avoided the problem of frequent updating of private keys of unrevoked users and greatly reduced the computing overhead of users. Theoretical analysis and experimental results show that the proposed scheme can resist chosen-plaintext attack under the Decisional Bilinear Diffie-Hellman （DBDH） assumption， and compared with other similar attribute based encryption schemes， the proposed scheme is more efficient， which supports online encryption， efficient user revocation， and has lower computational and storage overheads.