Abstract: In order to provide the scientific evidence for the method to determine different absorption capacity on formaldehyde of indoor ornamental plants. The author chose 4 species of indoor ornamental plants. Pot and soil were separated from the haulm and put into a self-designed fumigating box to conduct formaldehyde experiment. The author measured the change of formaldehyde and the plant leaf area before and after the experiment, and compared the ability of the 4 plants to absorb formaldehyde based on the reduction of formaldehyde in the unit leaf area. The results showed that: (1) their absorption capacity was as follows: Plectranthus tomentosa>Peperomia tetraphylla>Aspargus plumosus. (2) Tradescantia zebrine was particularly sensitive to formaldehyde, which could be used for monitoring formaldehyde. (3) When the formaldehyde concentration of 6 mg/m3 and 12 mg/m3, Plectranthus tomentosa, Peperomia tetraphylla and Aspargus plumosus absorbed the amount of formaldehyde with formaldehyde concentration multiply and multiply. But when the formaldehyde concentration was 24 mg/m3, Plectranthus tomentosa and Tradescantia zebrine on formaldehyde absorption rate declined gradually. While the Peperomia tetraphylla of formaldehyde absorption rate remained at a steady state.