Abstract: Meaning transfers and drifts in social interactions. In this process, some meanings are retained, some are lost, and some are changed. This phenomenon is very common when the process of court trial is transferred into its written judgment. The meaning of the courtroom discourse is multi-dimensional. In the process of forming the judgment, the meaning in courtroom discourse will be changed or lost to varying degrees due to the recontextualisation of the trials and the monomodality of the written judgment. From the perspective of social semiotics, along with the genre theory in systemic functional linguistics and the approach of multimodal discourse analysis, this paper analyses the effects of context, recontextualisation, semovergent and sonovergent resources on speech acts and events. It explores the generation and change of meaning in the transition from courtroom discourse to written judgment, as well as the factors that lead to these changes. The analysis shows that the courtroom discourse highlights the ideational meaning of the participants' reconstruction of case facts, the interpersonal meaning of expressing their attitudes and positions, and the textual meaning of identifying the relevant entities involved in the case, and that the written judgment, by means of retaining, adding or deleting, selectively transforms these three kinds of meaning to realize legal reasoning, persuasion, and judicial fairness and justice.