Abstract: The signal strength fluctuations on the spacecraft-to-earth link caused by solar wind turbulence will reduce telemetry performance. It is essential to establish a reliable deep-space communication link. The K-distribution model of the solar wind turbulence and strong scintillation channel of the telemetry link is established by analyzing the characteristics of the telemetry signal amplitude scintillation caused by the solar wind. Using the Laguerre orthogonal polynomial, the channel K distribution is approximated and studied, and a closed-form approximation of the binary phase shift keying (BPSK) bit error rate under the strong scintillation channel of solar wind turbulence is given. Numerical calculations show that the scintillation index has tremendous influence on the bit error rate, and the parameter β affects the K-distribution approximation and bit error rate of the strong scintillation channel of the strong wind, and choosing a smaller value is beneficial to reduce the KL divergence and bit error rate of the K-distribution approximation. At the same time, choosing a smaller parameter b, that is a smaller β as well, is helpful to reduce the bit error rate of the telemetry system.