Using comb laser pulses synchronized with the main pulse output by large laser facility as time fiducial to scale the reaction process between high power laser pulse and target is very important for the realization of precise measurement and simulation in the intense field experiment. We demonstrate a fiber multiharmonic time fiducial laser pulse generation system using optic-electric modulation and optical pulse stacking. A unit optical pulse with a width of 150 ps generated by modulation was stacked in a fiber stacker to form a 1053 nm comb pulse. The pulse was then amplified and frequency-converted to generate green (527 nm) and UV (351 nm) fiducials. The system can stably provide Shenguang-Ⅲ prototype facility with multi-frequency laser time fiducials which is essential for the precise physical experiment. In addition, the system is highly adaptive since it can generate fiducial signals with variable pulse intervals and amplitudes flexibly according to the requirements of different physical experiments.