The invention discloses a wireless sensor network grouping small data security distributing method. The method comprises the steps that a base station groups nodes according to the hop count from nodes to a base station; the base station randomly selects random number of the same number, generates a one-way hash chain for each group, and stores the orientation hash value of each hash chain on a corresponding grouped node; the base station preprocesses a data packet to be sent, and uses the orientation hash value on a hash chain to encrypt the predecessor value on the chain; the data packet and the predecessor value are combined to acquire a combined hash value, and a parameter representing the life cycle of the data packet to construct a data packet to be transmitted; a sensor node verifies the data packet; the data packet is parsed according to the group of the node, and then the legality is verified; if the data packet is data of another group, the data packet is directly forwarded; and if the data packet is a legal data packet, the data packet is accepted and a data item corresponding to the node is updated, otherwise the data packet is directly deleted.