Formaldehyde pollution from decoration materials may damage the museum objects on display, which is widely concerned. In order to evaluate the effectiveness of formaldehyde removal by absorbent materials, a closed test chamber was set up and the formaldehyde concentration in the chamber was measured. Formaldehyde was generated from solution or synthetic board, various absorbents were added and a formaldehyde concentration vs. time curve in the chamber was recorded. An evaluation method was established. Active charcoal and three chitosan-based absorbents were tested for their ability to remove formaldehyde. This work showed that air purification studies are best done with formaldehyde generated from synthetic board, which better reflects the true situation in museum environments. The absorb stability of absorbents could be used to compare and reflect the stability of absorbents.