A statistical analysis of multi-band type Ⅲ bursts observed with the spectrographes in the ranges of 625~1500MHz, 2600~3800MHz and 5200~7600MHz during the 23rd solar cycle (from July 2000 to September 2004) is carried out in the paper. The main statistical results,
e.g., distribution of type Ⅲ bursts, duration, frequency drift rate (normal and reverse slopes), degree of polarization and frequency bandwidth are given. The results indicate that the average values of the frequency drift rates and frequency bandwidths increase with the frequency. The average values of the durations and degrees of polarization are neither constant nor uniform varying over broad frequency extent. Most of type Ⅲ bursts are distributed within the range from 625 to 3800MHz, and decrease with the increase in frequency. This distribution result means that the places of electron acceleration and energy release are mainly within the decimetric range, and the characteristic of frequency range is possibly related with the magnetic configuration on decimetric wavelengths, and the position of the electron acceleration in the reconnection region of magnetic field nearby the place of the main flare. However, there are large number type Ⅲ bursts in the range of 5200~7600MHz. This diagnostic means that the place of electron acceleration is in the broad range of the corona. The radiation mechanisms of type Ⅲ bursts on centimetric-decimetric wavelengths most probably include the coherent plasma radiation or the emission processes of electron cyclotron maser.
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