Spatial TDMA(STDMA) is a remarkable media access method for multi-hop wireless networks and the slot algorithm is the key of a STDMA scheme. Traditional STDMA slot algorithms don't take the task difference of the nodes into consideration and treats the nodes equally. In this paper, a novel slot distribution algorithm is proposed. It supports the node applying several slots at one time according to its forwarding tasks, which is beneficial to the fairness and balance of the whole network and especially suits for the asymmetric or hierarchy networks.