The high post of Big Sima had a significant impact on the political system of Han Dynasty. It existed during the Chu - Han Battle instead of the Emperor Wu. There are three kinds of Big Sima, the senior general Sima, the promoted Sima, and the third Sima. Its existence and evolution reflects that the feudal official post Big Sima in Han Dynasty is becoming more and more eminent. In Han Dynasty, Big Sima and Grand Com- mandant were muturally changed their names, there were similarities and differences between them. In the Sepa- ratist regime of Han Dynasty, there existed the post of Big Sima with different features.%大司马一职两汉皆有，其位高权重，对汉代的政治制度具有重大影响。楚汉之争时已经有大司马职官，而非始于武帝时。两汉冠以“大司马”之名的职官有三种，即高级将领之大司马、加官之大司马和三公之大司马。其存在与演变反映了汉代大司马职官地位越来越高的演变趋势。汉代大司马与太尉曾相互易名、更改，其二者属官有相同之处，亦有不同的地方。在两汉时期出现的各种割据政权中亦存在大司马职官，且各自有着不同的特点。
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