We examine the tensile deformation of the smectic melt of a main-chain liquid crystalline polymer. A film molded in isotropic melt is heated to a smectic temperature of 60 degrees C and then stretched at selected strain rates. In the initial stage of strain below 100% (defined as {(l - l(0))/l(0)} x 100%), smectic layers align parallel to the stretching direction; i.e., polymer chains orient perpendicularly (so-called "perpendicular orientation"). This perpendicular orientation in the low-strain region is invariably observed at any strain rate. Upon succeeding elongation, however, two distinct types of orientation process are observed depending on the strain rate. On elongation at strain rates as low as 5%/min, the perpendicular orientation is improved until the sample breaks at 400% strain (process A). At a high strain rate of 100%/ min, in contrast, the perpendicular orientation initially observed is eventually altered to the "parallel orientation" with polymer chains lying parallel to the tensile axis (process B). In this case, the well-known necking takes place, and the sample breaks at an extremely large strain more than 3000%. These two distinct elongation processes are also dependent on temperature; processes A and B are observed in higher and lower temperature regions, respectively. On the basis of these data, the molecular orientation mechanisms in smectic field are discussed by coupling together the nature of smectic liquid crystal and dynamics of polymer chains.