The interaction of mixed polyether polyester blockcopolymer (MPEE) and 1

4-dicarbaz-ylcyclobutane (1

4-DCC) in the excited state and the ground state has been studied by measurement of fluorescence spectra. The results show that the fluorescence spectrum of 1

4-DCC was quenched by MPEE by formation of exciplex in chloroform solution. The quenching effect is folowing Stern-Volmer equation. Kq is obtained (7.0 ×109mol-1s-1) from S-V plot and r value of 1

4-DCC. Not only the monomer band of 1

4-DCC but also the exciplex hand of 1

4-DCC and MPEE were observed in the film of MPEE in which 1

4-DCC was dispersed. The co-mplexation of 1

4-DCC and MPEE in the ground state was proved by the appearance of long wavelength band in excitation spectrum. Analogously the quenching effect of dimethyl tereph-thalate (DMTP) and ethyleneglycal-p-phthalate (EGP) which is used as a model compound of hard segment of MPEE has been studied too. Furthermore. 1

4-DCC could be used as a flu-orescence probe molecule of MPEE. The structure and morphlogy of MPEE could be studi-ed by fluorescence technique.