We investigate methane(CH4), hydrogen peroxide(H2O2), and water vapor in the Martian atmosphere by the Planetary Fourier Spectrometer (PFS) onboard Mars Express spacecraft. Recently, methane is discovered in the Martian atmosphere. It is remarkable because its sources are potentially a geological and a biological activity on Mars. We observed Mars for constraint of the source of methane and the data analysis is on-going now. We attempt to derive vertical profile of methane with the PFS limb-geometry observation data. Hydrogen peroxide is one of the best tracers of oxidizer in the Martian atmosphere. We detected it by the PFS onboard MarsExpress. It was first time to detect hydrogen peroxide with an instrument onboard Mars explorer. The derived amount was very small (~40ppb), which is not enough to destroy methane in weeks or months. Since the observed lifetime of methane is weeks or months, is needs further research of the sink of methane.