Femtosecond time-resolved fluorescence spectra technique based on non-collinear optical parametric amplification is a new method for ultrafast spectroscopy research. In the present report, the authors discuss the dynamic range for amplifying fluorescence. The supercontinuum seed can be amplified linearly to its transient intensity. Due to large amplification ratio up to 107, small instability in pump pulse energy produces large fluctuation in final output amplitude. Here the authors introduce a method using cone emission as reference to overcome this difficulty. The results show significant improvement in fluorescence dynamics curve.