In this paper, we analyse the variations of microwave, X-ray and γ-ray burst spectra with time on 27 April 1981. By comparison between these curves of spectral indices and time profiles we find the following observational features: 1) The similar profiles consist of seven major pulses. It is shown that two sub-peaks of each pulse (only for No. 1-6 pulses) correspond each other. Besides, there are also two sub-valleys on the spectral curves of raido and X-ray bursts, but two sub-peaks of γ-ray burst, corresponding to two sub-peaks of time profiles; 2) During the rising phase-peak-decreasing part of each pulse for No. 1-6 pulses, the spectral indices of radio and X-ray emissions appear as soft-hard-soft and coincident between them, but the variations of indices for No. 7 pulse of radio and γ-ray bursts are consistent as hard-soft-hard while the indices of X-ray burst appear as soft-hard-hard. These observational features may be explained in terms of the stochastic electron acceleration in the turbulent plasma and by osillating solution of electron kinetic equation in a pulsed injection.