In the multi-agent social network, the traditional task allocation models generally adopt allocation mechanism that directly orients to task performers. They do not consider the huge impact of social network structure on the performance of allocation, and seldom thoroughly research the allocation mechanism for the unreliable society. Aiming at these problems, this paper firstly designs a collaborative organization model according to the hierarchical and layering methodology, then proposes a community oriented task allocation model for software-hardware syncretic systems. In the process of model research, the paper develops a community trust evaluation mechanism based on direct trust and community reputation, a community node selection mechanism based on trust degree and physical ability of community, a load balancing mechanism which is applied to the task allocation in interior community, and a task redistribution strategy based on the context of community resources. The results of experiments show that the proposed model has better allocation performance and robustness compared with other classical models, and also validate that the load balancing allocation mechanism and the redistribution strategy can not only effectively improve the allocation performance but also reduce the communication density of the social network.