The invention discloses a formaldehyde detection system for building decoration. The formaldehyde detection system for building decoration comprises: a data storage module configured to store formaldehyde content data of decoration materials; a formaldehyde detection module configured to perform formaldehyde content detection for the decoration materials; a monitoring module configured to monitorthe air formaldehyde content in the decoration field; a data processing module being in signal connection with the data storage module, the formaldehyde detection module and the monitoring module andconfigured to receive the data information transmitted from each module and perform processing; a comparison module configured to determine whether the data of the data processing module generates a formaldehyde content exceeding phenomenon or not; and an alarm module being in signal connection with the comparison module and configured to emit alarm when the formaldehyde content exceeds the standard. The method solves the problem that formaldehyde pollution cannot be effectively monitored before and after decoration and in the decoration process in the prior art, and achieves the purpose thatthe whole process can be effectively monitored before and after decoration and in the decoration process.