A combinatorial optimization problem, namely $k$-Cardinality Tree Problem, 
is to find a subtree with exactly $k$ edges in an undirected graph $G$, such that the sum of edges' weights is minimal. 
Since this problem is NP-hard, though many heuristic and metaheuristic methods are widely adopted, 
the precision of these methods is not well enough. 
In this paper we shall give a Memetic Algorithm based on Tabu Search for solving this problem. 
The crossover in Memetic Algorithm acts as a powerful diversitification strategy, which enlarges search area effectively. 
The experimental results show that the proposed algorithm is superior to existing algorithms both in precision and computing time. 
We arrive at a conclusion that a well designed hybrid metaheuristic algorithm is efficient for solving the $k$-Cardinality Tree Problem.