Abstract: X-ray real time imaging method was adopted to nonde-structively test the complex structure welding parts of titanium alloys, the spatial position of tiny flaws was determined based on the line profile distribution of flaws position, and a formula which could calculate the burial depth of flaws was obtained. According to the characteristic of abnormal peak and abnormal slant-concave flaw, an automatic extraction algorithm of projection distance was presented individually. Experimental results showed that the above algorithm can figure out the projection distance very well and can determine the spatial distribution features of the flaws.