A mid-infrared (MIR) difference-frequency generation(DFG) technique based on the synchronous pulse induction was proposed and implemented, where a high-speed photodiode detector was used to convert the pump optical pulse into an ultrashort electrical signal for driving a high-bandwidth amplitude modulator on a tunable continuous-wave laser, thus leading to the stable timing synchronization between the dual-color pulses. The nonlinear DFG process with synchronous pulse induction was utilized to effectively reduce the pump threshold for the optical parametric down-conversion. Consequently, watt-level MIR ultrashort pulses could be generated with a maximum pump conversion efficiency up to 60%. The central wavelength could be tuned from 3000 to 3175 nm. Thanks to the all-polarization-maintaining fiber architecture, the instability(STD/MEAN) of the average power was as low as 0.07% in one hour, exhibiting a superior long-term stability. Additionally, the optical-electrical-optical conversion was used to implement the high-precision pulse synchronization with the presented scheme, which eliminated the requirement for the complex feedback circuit. The system was thus featured with simple structure, plug-in operation, and strong robustness, which would pave the way to promoting the MIR light source in field applications.