The invention discloses a circuit for size comparing in multiple data. Relative position of the data is not changed, and relative size of the data in each frame is indicated with a serial number. An assembly line structure is adopted, the data is received and compared simultaneously, and comparison is completed while the data is received. Multiple data frames received consecutively can be compared consecutively, extra insert waiting is not needed, and the circuit is well adapted to common interface characteristics of communication and signal processing.