Thank panic mode very much for the answer! In fact there are other motion commands before the SPLINE:
Code
PTP HOME
LIN {X 290.1,Y 348,Z 410.2,A 39.4,B 5.6,C 134.7} C_DIS
SPLINE
SPL {X 0,Y 638.1,Z -0,A -0,B 35.3,C 120}
SPL {X 42.6,Y 595.5,Z 60.2,A 1.2,B 34.7,C 120.7}
SPL {X 73.5,Y 564.6,Z 104,A 3.5,B 33.5,C 122}
SPL {X 95.4,Y 542.7,Z 134.8,A 5.8,B 32.3,C 123.2}
SPL {X 113.4,Y 524.7,Z 160.4,A 8.1,B 31,C 124.4}
ENDSPLINE
I suppose LIN {} C_DIS only approximates the point {X 290.1,Y 348,Z 410.2,A 39.4,B 5.6,C 134.7}, it has no effort on the SPLINE. Am I right?
Then how to make the first point of the SPLINE to be approximated?