A 3D projection system based on complementary multiband bandpass filter (CMBF) is proposed in this paper, which enables viewers to gain 3D experience through special glasses. Different from the time-multiplex or the spatial-multiplex system, it is a spectrum-multiplex system using pairs of CMBFs. The three pairs of complementary bandpass of a pair of CMBFs can be designed to cover the three spectrum ranges of RGB individually and in each pair the two bandpass nearly do not overlap. In this paper, a 3D projection system is built from two ordinary projec-tors and its spectrum, brightness and crosstalk have been measured. The average crosstalk is 3%, meeting the ba-sic requirement of crosstalk in 3D display which is less than 10%.