Abstract The Internet of Things (IoT) is expected to support a wide variety of devices with different transmission reliability requirements. Channel codes with the unequal error protection (UEP) property are rather appealing for such applications. As the first provably capacity-achieving codes, polar codes have excellent error-correcting performances over a wide range of block lengths with low encoding and decoding complexities, which makes these codes well-suited for the energy-constrained IoT applications. Polar codes with unequal error protection are desirable. However, the UEP property of polar codes has not been explored explicitly in existing works. In this paper, a construction method for UEP polar codes is proposed based upon a novel selection rule of bit-channels. Refreezing and reselecting operations are employed to enable the UEP property for polar codes. The upper and lower bounds on the block error rate (BLER) of each data block are derived. Simulation results show that the proposed codes can provide a good performance of unequal error protection.