ObjectiveTo study the distribution and change of microbial population of clinical isolated bacteria from a hospital in recent 10 years. MethodsBacterial culture results of  60 846 clinical samples (blood, urine ,throat swab,sputum,stool , vagina swab,and sterile body fluid) from  inpatients and outpatients between January,1999 and December,2008 were analysed retrospectively.ResultsThese isolates included 67 genus 207 species 18 674  strains of bacteria, the isolation rate was 30.69%(18 674/60 846), the ratio of gramnegative bacillus to grampositive coccus and fungus was 54.42∶32.21∶11.56. The major bacteria were Salmonella paratyhi A, Viridans streptococci, Escherichia coli, yeastlike fungi ,coagulase negative Staphylococcus and Staphylococcus aureus. The proportion of gramnegative bacillus rose obviously, so did the opportunistic pathogens.  The isolation rates of Viridans streptococcus and enteric pathogens and Salmonella paratyhi A  decreased (P<0.01). ConclusionChange in  floral  is in accordance with fundamental characteristics  of presentday infection; The increase of opportunistic pathogens  is disadvantageous to the prevention and treatment of multiple  infectious diseases.