Abstract: The invention provides a safety lock for zipper bags, comprising a first pull block with a locking bar and a second pull block with a locking frame. Said locking bar is inserted into the locking frame to link the first pull block with said second pull block; said second pull block is further equipped with a release unit for detaching the locking bar from the locking frame. A slot is formed between said release unit and top surface of the second pull block. In the invention, the locking bar and the locking frame can connect and lock the two pull blocks which can be unlocked by pressing the pressing portions with certain force. Children are unable to open the zipper bag easily. Therefore, the invention can prevent children from mistakenly opening the zipper bag effectively and avoids loss of important documents and accidental ingestion of medicines.