Large two-photon absorption cross section ora novel compound trans-1,3,5-tri-(4-N,N-dimethylaminobenzylstyryl)- ＝ 10-47 cm4/(photon.s) by using a acetylacetone is measured to be σ2 ＝ 8.4 × 10-20 cm4/GW or σ2 1.594 × 1064nm Nd:YAG laser with 35ps pulse width based on the intensity-dependent transmissivity measurement. The frequency upconversion fluorescence is observed by two-photon laser pumping. This material is an ideal candidate for optical limiting and upconversion fluorescence.