The upconversion and optical power limiting properties of a new organic dye trans 4 [4' (N hydroxyethyl N ethylamino)styryl] N methylpyridinium p toluene sulfonate (abbreviated as HEASPS thereafter) in DMF are reported in this paper. The two photon absorption cross section of HEASPS at 1064 nm is measured to be σ 2=4.7×10 -48 cm 4·s/photon by using a Z scan system. The linear absorption, single photon induced fluorescence, two photon induced fluorescence and two photon pumped upconversion lasing properties are studied. There is a red shift for the central wavelength of the two photon induced fluorescence compared with that of the single photon induced fluorescence and a blue shift for two photon induced lasing compared with two photon induced fluorescence. These phenomena can be explained by using the re absorption effect. Intense upconversion lasing at 626 nm is obtained pumped by a mold locked Nd:YAG ps pulse laser operating at 1064 nm. The upconversion efficiency from the pump efficiency from the absorbed energy to the upconversion energy is 26%.