We demonstrate a continuously wavelength-spacing-tunable and high-power multiwavelength fiber optical parametric oscillator based on the multiwavelength idler-output technique. The laser cavity for multiwavelength idler outputs is constructed by a pumped highly-nonlinear dispersion-shifted fiber as parametric gain medium, two highly-reflective chirped fiber Bragg gratings (CFBGs) and a superimposed CFBG as comb-like filter. At a pump power of 1.1W, the idler output of 10 wavelengths around 1.56μm is achieved with a wavelength spacing of 0.39nm. The wavelength spacing can be continuously tuned from 0.39 to 1.0nm by utilizing a cantilever beam-based chirp tuning method to change the FSR of the superimposed CFBG. Our experimental results show that the designed multiwavelength idler-output scheme can significantly increase the multiwavelength output power with a total output power of 98mW and each idler-channel power of 16.3mW.