The invention discloses combined particle sound attenuation units. Each combined particle sound attenuation unit comprises a hollow base in the shape of a square column. The bases are made of particle sound absorption plates; annular grooves are formed in the outer side walls of the bases; the annular grooves are filled with sound absorption materials; the annular grooves can be spliced with one another to form cavities when the bases are combined with other bases. The invention further relates to a sound attenuation building block. The sound attenuation building block comprises the combined particle sound attenuation units which are spliced with one another. The combined particle sound attenuation units and the sound attenuation building block have the advantages that the combined particle sound attenuation units and the sound attenuation building block are environmental friendly; secondary pollution can be prevented; the combined particle sound attenuation units and the sound attenuation building block are good in weather fastness; sound absorption coefficients are good in stability; the combined particle sound attenuation units and the sound attenuation building block are free of environmental influence; excellent sound attenuation effects can be guaranteed even if the combined particle sound attenuation units and the sound attenuation building block are used for a long time.