Abstract: Existing policies promote the participation of new market players on the distribution side in the wholesale electricity market. However, since the wholesale market does not take into account the distribution system security constraints, the delivery of the awarded power of new market players may cause distribution system security issues. Meanwhile, due to the coupling of the transmission and distribution systems, the relationship between the locational marginal price in the wholesale market and the offer strategies of new market players is more complex. These characteristics make the offer decision problem of new market players in the wholesale market very challenging. This paper proposes an approach to offer decision making for new market players in the wholesale electricity market. While optimizing the offer strategy, the proposed approach considers the impact of distribution system security and the coupling characteristic of transmission and distribution systems on the offer strategy. Then, this paper establishes a security constrained strategic offer model for new market players in order to ensure the safe and reliable delivery of the awarded power on the distribution side. Next, considering the influence of the rival offer behavior model on its own offer strategy, the bounded rationality model is used to describe the rival offer behavior more rationally. The paper constructs the implicit expression of the locational marginal price by simulating the market clearing and optimizes the offer strategy. In order to reduce the solving difficulty, the model is transformed into a two-stage robust optimization problem with the lower implicit constraints, which is solved by using the column and constraint generation method. The case studies demonstrate the effectiveness of the proposed approach.