Grooming can increase multicast traffic request sucessful transmission probability and improve fiber link bandwidth utilization. But it certainly increases the network cost and complexity that all nodes are configured as grooming node in WDM network. Grooming node selection strategy was studied in the sparse grooming network. A grooming node selection strategy based on smallest cost largest degree was proposed. According to difference of grooming node function and non-grooming node function, the sparse grooming transmission method was improved to transmit the request for multicast request in the sparse grooming network. Lastly, according to the network′s blocking probability limit, a sparse routing method, integrated the node selection strategy with the smallest cost largest degree and multcast traffic grooming transmission method,was put forward to meet the multicat request with minimal grooming nodes. The simulation results show that the proposed strategy method can save number of grooming required nodes, optimize the location of grooming nodes and decrease the network node construction cost when network has given number of wavelengths per fiber and given transceivers of node in the sparse grooming network.