Abstract: Abstract For deep space communication paths close to the sun causing solar scintillation of radio waves and increasing bit error rate (BER), the approach of choosing the signal bandwidth in the non-frequency selective and slow fading channel with maximum time was proposed. The deep space communication channel model was built based on Rician fading channel model. The statistical characteristics of the amplitude, the coherence time and the coherence bandwidth of the channel were used. The difference among solar scintillation, mobile multipath and ionosphere scintillation was compared. Based on the change of the coherence time and coherence bandwidth with solar elongation angle, the time-selective and frequency-selective characters were determined.Simulation results show that at different little solar elongation angle, especially the small one, the BER of the signal bandwidth chosen by the proposed approach is better than the BER of other signal bandwidth.