Ultrashort travelling wave amplified spontaneous. emission(A8B)is generated by transversal synchronizing pumping scheme with gradient distribution of pumping energy. 50 ps light pulses are generated by nitrogen laser pumping and 8 to 15 ps pulses generated by frequency doubled and mode-looked Nd:YAG laser pumping. The pulse shape and spectrum of the travelling wave ASE as well as the non-travelling wave ASE are measured by means of streak camera and optical multichannel analyzer. The computer simulation on the temporal behaviour of the travelling wave ASE is pressented and the calculation is in good agreement with the experimental results.