Objective：To evaluate the antimicrobial activity of portland cement（PC），mineral trioxide aggregate（MTA） and glass ionomer cement（GIC）against three microorganisms：candida albicans，escherichia coli，streptococcus mutans through the Agar diffusion method. Methods：The sealers under study were handled according to the manufacturer’s instruction. All sealers were handled with diameter of 5 mm and thickness of 1 mm then placed in the wells which contains 1.5×108 CFU/mL microorganisms suspension of candida albi－cans，escherichia coli and streptococcus mutans，respectively immediately after being mixed. After the sealers set，the agar plates were incubated at 37 ℃ for 24~48 h to allow the microorganisms to grow and reagents to diffuse through the culture medium. After incuba－tion，diameter of inhibition zones was measured. Results：No antimicrobial activity of all the three materials was observed on strepto－coccus mutans. No inhibition zone of GIC was observed on the three microorganisms. Diameter of inhibition zone of PC on candida al－bicans was bigger than that of MTA with significant difference between two groups（P=0.002 9）. Conclusions：PC could effectively in－hibit the growth of candida albicans and escherichia coli，therefore PC is considered to have certain antifungal and antibacterial prop－erties.