Abstract: Measurement of squareness of the copped pipe end is regarded as a key item of steel pipe visual inspection. After being expanded, the end of the pipe is slightly“belled”. In this case, the pipe end squareness as measured with the steel square is not the actual value, neither the one as measured with the wire weigh method in the event that the inspection table is not quite horizontally leveled. Analytical calculation shows that thanks to the improved measurement method, the pipe end squreness can be precisely checked by either the steel square or the wire weight.