Given the issue that existing optical orthogonal frequency division multiplexing(OFDM)with index modula-tion(OOFDM-IM)struggle to adapt to channel variations,which results in limitations on transmission rate.A threshold optimization model aimed at maximizing transmission rate was constructed.By dynamically identifying the optimal M-QAM modulation switching threshold,an optical OFDM adaptive indexing modulation scheme was proposed.After a de-tailed introduction to the mapping principle of the signal,the optimal threshold and theoretical bit error rate under differ-ent turbulence intensities were derived.The simulation results show that compared with traditional OOFDM-IM schemes,the proposed scheme significantly enhances transmission rate while satisfying the target bit error rate.