Scene Graph Generation (SGG) provides basic language representation of visual scenes, requiring models to grasp complex and diverse semantics between various objects. However, this complexity and diversity in SGG also leads to underrepresentation, where part of test triplets are rare or even unseen during training, resulting in imprecise predictions. To tackle this, we propose using the SGG models with pretrained vision-language models (VLMs) to enhance representation. However, due to the gap between the pretraining and SGG, directly ensembling the pretrained VLMs leads to severe biases across relation words. Thus, we introduce LM Estimation to approximate the words' distribution underlies in the pretraining language sets, and then use the distribution for debiasing. After that, we ensemble VLMs with SGG models to enhance representation. Considering that each model may represent better at different samples, we use a certainty-aware indicator to score each sample and dynamically adjust the ensemble weights. Our method effectively addresses the words biases, enhances SGG's representation, and achieve markable performance enhancements. It is training-free and integrates well with existing SGG models.