  A mapping study of IRAS 05553+1631 was performed with 12CO J=3-2 and 13CO
J=2-1 lines observed by the KOSMA 3 m-telescope. A core with a size of 0.65 pc
and with a LTE mass of 120 M\odot was defined by the mapping with 13CO J=2-1
line. We have identified a bipolar outflow with 12CO J=3-2. For accuracy in the
calculation of outflow parameters, overcoming the projection effect is
important. We propose a new method to directly calculate the inclination-angle
{\theta}. We establish two basic equations with the help of outflow contour
diagram and finally obtain the "angle function" and the "angle equation" to
derive {\theta}. We apply our method to the outflow of IRAS 05553+1631, finding
that {\theta}blue is 73\circ and {\theta}red is 78\circ. Compared to the
parameters initially estimated under an assumption of 45\circ
inclination-angle, the newly derived parameters are changed with different
factors. For instance, the timescales for the blue and the red lobes are
reduced by 0.31 and 0.21, respectively. Larger influences apply to mechanical
luminosity, driving force, and mass-loss rate. The comparisons between
parameters before and after the correction show that the effect of the
inclination-angle cannot be neglected.
