Employing multiple paths for achieving high capability and robustness has some obvious benefits. New wireless technologies are giving more Internet access modes for notebooks and smart phones. However, most multipath protocols may not get acceptable throughput if reliable transmission is guaranteed. For some cases, the situation may even worse than using single path only. The main reason has strong relationship with the principal of multipath transmission. Motivated by these facts, specific analytical mechanisms are proposed to analyze the potential problems which may lead to serious performance decrease. Following that, we investigate how to use multiple paths legitimately when network environments are fluctuating. In our simulation, topologies for multiple paths and single path are set up for evaluating our analytical methods. Some distinguished scenarios are chosen from different perspectives. The results have revealed some throughput critical conditions and could be helpful in designing scheduling schemes for multipath protocols.