Based on the model bilateral investment treaties (BITs) and typical international investment agreements(IIAs)of the U.S. and European styles, this paper analyzes state-owned-enterprise (SOE)-related provisions from both historical and horizontal perspectives to investigate the SOE competitive neutrality obligations in IIAs. The conclusions are as follows. In terms of the definition of“investor”, both cover state-owned and private enterprises, thereby offering equal treatment in principle. However, in U.S. IIAs, additional obligations apply to SOEs. In terms of the subject of a contracting party’s obligations, the U.S. IIAs cover SOEs exercising delegated regulatory, administrative or other governmental authority. In terms of MFN obligations, the U.S. IIAs definitely exclude government subsidies or grants on the one hand, while formulate SOE competitive equality provisions on the other. Since the European Commission replaced EU members to negotiate IIAs after the Lisbon Treaty, the European-style IIAs have gradually followed the U.S. model and the above differences are shrinking.