A transformed human dental pulp cell(LSC) was made to assess thecytotoxicity of dental resin monomers with MTT assay,NR assay and ALPase activity assay. L- 929 cells were used as comparative cell line. The sensitivity amongMTT,NR and ALPase activity assays and between two types of cells were investigated. The relationship of ALPase activity to two colorimetric assays was also evaluated. According to IC50 and statistics analysis on cytotoxicity curve,there were significance differences between MTT and NR assay or both cell lines for TECDMAmonomer (P＜0．005). MTT assay showed lower sensitivity than NR assay in twokinds of cell for both monomer,and LSC cells presented less sensitivity than L-929cells for TEGDMA monomer. The ALPase activity assay revealed the highest sensitivity among the three tested assays. There was a positive relationship between thecontent of ALPase activity and cytotoxic response of the other two assays. The results indicated that the sensitive degree of test assay or cell line may differ from thetest chemicals. MTT assay may be more suitable for screening a wide large of unknown tested materials due to its ralative less viariation with cell lines and moderatesensitivity. A sensitive human dental pulp cell (LSC) was made to assess the cytotoxicity of dental resin monomers with MTT assay, NR assay and ALPase activity assay. L-929 cells were used as a comparative cell line. The sensitivity among MTT, NR and ALPase activity assays and The relationship of ALPase activity to two colorimetric assays was also evaluated. According to IC50 and statistics analysis on cytotoxicity curves, there were significance difference between MTT and NR assay or both cell lines for TECDMAmonomer (P <0 .005). MTT assay showed lower sensitivity than NR assay in twokinds of cell for both monomer, and LSC cells presented less sensitivity than L-929 cells for TEGDMA monomer. The ALPase activity assay revealed the highest sensitivity among the three tested assays. There was a positive relationship between the content of ALPase activity and cytotoxic response of the other two assays. The results indicates that the sensitive degree of test assa MTT assay may be more suitable for screening a wide large of unknown tested materials due to its ralative less viariation with cell lines and moderate sensitivity.