In order to realize the diagnostics for synchronization of multi-ultrashort pulses, a method to diagnose the synchronization of multi-ultrashort pulses is provided and tested. Taking two beams of picoseconds ultrashort pulses for example, the time division multiplexing method is used. Based on the cross-correlation method, the time synchronization between these two pulses is realized at first. Then, the phase difference of the beams within the range of time synchronization is adjusted. By monitoring the focal spot on far- field can implement the phase synchronization of two pulses. In this scheme, the regulation precision of temporal synchronization and phase synchronization is 6.7 fs and 0.007 π, respectively. The adjustable range of temporal and phase module is 333 ps and 150 π, respectively. The experimental results show that by using this diagnostics scheme the diagnostics for synchronization between two ultrashort pulses can realized.