Abstract: Variation of microbial communities in inoculated and natural composts was studied with the traditional incubation method and the PCR-DGGE technology.Results indicate that 1)with the traditional incubation method,the population of microbes showed a wave-like curve,i.e.up-down-updown,in both composts and bacteria dominated the microbes in population,while 2)with the PCR-DGGE technology,the population showed a similar curve,though different microbial populations dominated at different composting stages.The DGGE graph showed abundance of bands and none in predominance during the warming up phase;the number of bands decreased but predominant bands appeared during the high temperature phase,suggesting that thermophiles were dominating microbes during this phase;the number of bands increased again during the cooling phase;and the number of bands dropped and no one remained in dominancy during the maturation phase,suggesting that the microbes were getting less in populations and their metabolism was levelling off during this phase.(3)The DGGE spectrum also showed that inoculated strains assumed predominance during the high temperature phase,and inoculation increased the total count of microbes,enriched microbial diversity and accelerated succession of microbes during composting,thus shortening duration of the composting process.