Objective:To investigate the color difference of natural teeth and two types of metal ceramic restorations when the light source changed. Methods:According to the CIE L*a*b* color scale ,on the condition of illuminants of D65,A and CWF,the color parameter and spectral reflectance curves of natural teeth and two types of metal ceramic restorations of A2 shade were measured with a spectrophotometer(PR-650). Metameric index was calculated to determine the metameric color differences between natural teeth and two types of metal ceramic restorations. Results:CIE L,a,b values were influenced by the different illuminants in both natural teeth and two types of metal ceramic restorations. The spectral reflectance curves for natural teeth and metal ceramic restorations of A2 shade differed greatly,while there were more than 5 crossing points in each curve. The metameric index between natural teeth and tow types of metal ceramic restorations under illuminant A were 2.03 and 2.46,respectively,2.84 and 2.89 under illuminant CWF. The metameric index between metal ceramic restorations of different kinds were 1.09 under illuminant A,and 0.40 under CWF. Conclusion:Color differences were found between natural teeth and metal ceramic restorations of A2 shade relative to the different illuminants. The metameric effect between natural teeth and metal ceramic restorations of A2 shade is significant.