The total internal partition sums of formaldehyde were calculated by Fortran90 program. At the same time the line intensities of 000010-000000 and 100000-000000 transition bands of formaldehyde at several temperatures ranging from 296 to 3000 K were computed. Results showed that at this temperature range the agreement between the calculated line intensities and those extrapolated from HITRAN database is fairly good, which provides a strong support for the calculations of partition function and line intensity at high temperature. Then, the line intensities and spectral simulations at the higher temperature 4000 K are presented.