In this study, we design a transmitter compatible with five modulation formats based on dual IQ modulators. We develop a schematic of a multimodulation format compatible transmission system in the simulation software. The simulation results show that this system is compatible with OOK, BPSK, DPSK, QPSK, and DQPSK. We also process and develop multimodulation format compatible transmission hardware and conduct experimental tests on the performance data of the system. The simulation results show that the five formats can be compatible with the same IQ modulator. The Q value decreases as the modulation level increases. In contrast, the EVM value increases as the modulation level increases. The experimental results show that this hardware system can support more than five compatible formats; high-speed communication sensitivity is high, and the sensitivity is close to -39.8 dBm (40 Gbit/s@10^-7). The rate at each format is adjustable in three levels (2.5, 5, and 10 GBaud), and the communication bit rate can reach 40 Gbit/s.