GradeAssist is the world's first AI essay grading assistant designed specifically for teachers. By utilizing customized grading criteria, personalized AI feedback and annotations, plagiarism detection, grade estimation, and AI writing detection tools, GradeAssist helps teachers complete essay grading more efficiently and accurately. By reducing grading time, enhancing grading consistency, and promoting academic integrity, GradeAssist significantly alleviates teachers' workload while improving students' writing skills.