The absorption spectra of H2CO were recorded at room temperature with a typical equivalent sensitivity of 3.61 × 10-6cm-1Hz-1/2 by utilizing a QCL based gas detection set-up. Relative frequency calibration based on F-P etalon and absolute frequency calibration based on CH4 spectrum are calculated and shown in this paper. Frequency tuning spectra are also measured and processed when changing the operation temperature from -15℃ to 20℃ with increment of 5℃. As nonabsorbent gases, He, Ne, Kr, O2 and CO2 were used to determine the line intensity of H2CO line centered at 1253.14392cm-1. Buffering spectrum in N2 and the corresponding statistical residuals were given to show broadening characteristics and the difference between the observed absorption data and the expected Voigt fit value with increasing the pressure of buffer gas.