The joint iterative decoding assisted (JIDA) algorithm is different from the pilot assisted algorithm. It does not use the pilot signal, but uses the decoding output of the decoder to estimate the carrier frequency offset. Because the decoder can effectively reduce the impact of noise exists in the received signal, the JIDA algorithm has a good performance in satellite IoT transmission system which is in a low signal noise ratio (SNR) environment. However, the JIDA algorithm is difficult to apply in the case of short frame length because of poor estimation accuracy. In this paper, we propose a method that can effectively improve the estimation accuracy of the JIDA algorithm which is an important consideration in narrowband system by using multi frame accumulation while keeping the estimation range. At the same time, we use discrete Fourier transform (DFT) to simplify the estimation expression and reduce the complexity of the algorithm. The simulation results show that the proposed improved JIDA algorithm has higher estimation accuracy than the pilot assisted algorithm at low SNR.