The invention relates to a step-temperature closed emission method for simultaneous determination of formaldehyde emission characteristic parameters of building materials at multiple temperatures. Based on a adsorption potential theory and a Henry's law, a functional relationship between a separation coefficient K and an initial dissipative concentration C0 is established, and an analytical formula of the equilibrium concentration Cequ of formaldehyde in the closed environment is derived. A sealed environment cabin is used to maintain a constant temperature and a humidity space, and the building material samples are subjected to formaldehyde emission test, and the formaldehyde hourly concentration and equilibrium concentration at the initial temperature are measured. The temperature is then raised and the corresponding new equilibrium concentration is measured. The above operations can be repeated in sequence to obtain a formaldehyde equilibrium concentration value at multiple temperatures. The nonlinear fitting is carried out on the formaldehyde hourly concentration at the initial temperature, the K at the temperature can be determined. When the Cequ of the building material at other temperatures is known, the K at the corresponding temperature can be quickly obtained by the ratio of the equilibrium concentrations, and the corresponding C0 can be calculated. The method greatlyimproves the measurement efficiency of formaldehyde emission characteristics.