This paper addresses the distributed flocking control problem based on adaptive sliding mode control for a networked uncertain Euler-Lagrange(EL) system with parameter uncertainties and unknown external disturbances. The proposed algorithm uses both adaptive sliding mode control(SMC) and adaptive control law to compensate for the unknown external disturbances and linear parameterizable uncertainty terms, respectively, thus avoiding the requirement of prior knowledge of the external disturbances. Theoretical analysis shows that the adaptive gains employed in the algorithm remain bounded while the agents achieve the desired collective flocking behavior. In addition, the proposed algorithm considers both leader tracking control and the region control, and gives the condition for collision avoidance. Finally, numerical simulations verify the theoretical results of the proposed algorithm.