Nonlinear fiber effects are useful for controlling optical spectra in a wide variety of ways. Here, we report the demonstration of freely controllable, intense spectral peaking using a high-resolution spectral filter with a liquid-crystal spatial light modulator and nonlinear fibers. A large enhancement of spectral peak components by more than a factor of 10 was achieved by employing phase modulation. Multiple spectral peaks with an extremely high signal-to-background ratio (SBR) of up to 30 dB were generated simultaneously in a wide wavelength range. It was shown that part of the energy from the whole pulse spectrum was concentrated at the filtering part and constructed the intense spectral peaks. This technique is very useful for highly sensitive spectroscopic applications and comb mode selection.