Due to the low computational efficiency and storage space of the microprocessors used in terminal small devices of IOT (Internet of Things), a lightweight encryption algorithm based on elliptic curve cryptography technology was proposed in this paper. Firstly, two different points on determined elliptic curve were chosen randomly to generate the key. Secondly, the scalar multiplication was replaced by the point addition and subtraction, double point operation in the process of encryption. Finally, the ciphertext was salted. The experimental results show that, compared with ElGamal algorithm based on ECC, the ciphertext size of the method reduces by 25% and the encryption rate increases by 200%.