The invention relates to a method and 
system for calibrating the parallelism of an incongruous turning 
light pipe based on double-mirror splicing. The method comprises the following steps: step 1, setting a 
system; step 2, adjusting 
azimuth angles and 
pitch angles of reflectors of the first 
plane mirror device and the second 
plane mirror device through the same high-precision gyro 
theodolite respectively, so that north orientation values L and 
pitch values I of the two reflectors are the same, and double-mirror splicing is realized; step 3, setting a to-be-measured incongruous 
reflex light tube, using the high-precision gyro 
theodolite in the step 2 to measure an orientation value L1 and a pitching value I1 of the reflector of the second plane reflector device, keeping the position of the high-precision gyro 
theodolite unchanged, rotating a sighting part, measuring an 
azimuth value L2 and a pitching value I2 of a reflector of the first plane reflector device by using a high-precision gyro theodolite through the incongruous 
reflex light tube to be measured, and calculating an 
azimuth error 
delta L and a pitching error 
delta I according to a formula 1: 
delta L = L1-L2-180 degrees and a formula 2: delta I = I1 + I2-2ia-180 degrees.