Signal change strategy plays a primary role in the development of sensitive assay system. Deep insights into multiple signal responses will benefit the assembly of efficient sensors. Herein, we have developed a multifunctional fluorescent probe 2-((5-(9-phenyl-9H-carbazol-3-yl)thiophen-2-yl)methylene)malononitrile (SO–CN) for the detection of N2H4 and H2S with different emission channels. Initially, a broad band at 604 nm has been monitored and an orange-yellow fluorescence has been observed in DMSO/PBS system (3/2, v/v, pH 7.4). After treating with hydrazine (N2H4), only N2H4 can give rise to the special changes of SO–CN by the signals of ratiometric fluorescence (F442/F604) and colorimetric signals (bright yellow to colorless) with a low detection limit (42.5 nM). Moreover, the fluorescence intensity ratio F532/F604 of SO–CN exhibits an excellent linear equation with the concentration range (NaHS) from 0 to 400 μM (detection limit = 0.77 μM). In this way, SO–CN can be employed to recognize N2H4 and hydrogen sulfide (H2S) via the same excitation wavelength and different emission performance. The discriminative sensing behaviors of SO–CN for N2H4 and H2S are assigned to two mechanisms, which can be verified by 1H NMR spectra, HR-MS spectra and density functional theory (DFT) calculation. Therefore, this molecular framework has pave new way for the detection of new target species with functional group controls.