In order to improve the performance of free space optical/radio frequency(FSO/RF) hybrid communication links, one modulation method combining hybrid low density parity check (LDPC) coding with subcarrier phase shift keying/quadrature amplitude modulation(PSK/QAM) was adopted. Bit error ratio(BER) performance of hybrid systems with different transmission ratios was simulated and analyzed. BER data of single link and mixed link transmission schemes under different channel conditions were obtained. The results show that subcarrier binary phase shift keying (BPSK) modulation used in weak, moderate and strong turbulence can obtain gain about 4.4dB to 5.2dB compared with on-off keying (OOK) modulation. One soft-switching modulation scheme of hybrid LDPC coding and subcarrier BPSK/16QAM is adopted. When the ratio is adjusted to 1∶1 and 3∶1 according to link state, performance gains about 0.3dB to 7.4dB can be obtained under different turbulence intensities. This research result has important reference value for improving all-weather efficient and reliable transmission performance of FSO/RF hybrid communication systems.