Received signal strength(RSS)-based approach of wireless localization is easy to implement at low cost. In practice, exact positions of anchors may not be available. This paper focuses on determining the location of the source in the presence of inexact position of anchors based on RSS directly. This study at first uses Taylor expansion and a min-max approach to get the approximate maximum likelihood estimator of the source coordinates. Then this paper proposes a relaxed semi-definite programming model to circumvent the non-convexity. This paper also proposes a rounding algorithm concerning both the inexact source location and the inaccurate anchor location. Experimental results together with analysis are presented to validate the proposed method