When　time　reversal　method　is　used　for　nondestructive　testing　of　the　pipeline　with　ultrasonic　guided　wave,　the　energy　can　be　focused　on　the　defect　both　in　time　and　spatial　domain.　But　the　inspection　of　defects　with　different　axial　length　and　circumferential　angle　need　to　be　further　studied.　Time　reversal　numerical　simulation　method　was　employed　to　visualize　focusing　process　of　guided　waves　in　pipes.　The　varying　of　reflection　coefficient　of　through-thickness　crack　before　and　after　the　time　reversal　method　was　studied.　Results　shown　that　reflection　coefficient　after　time　reversal　method　was　much　bigger　than　that　before　it　when　circumferential　size　was　smaller,　and　it　tended　to　be　equal　when　circumferential　size　increased.　When　crack　axial　length　increased　from　λ/100　toλ,　reflection　coefficient　after　the　time　reversal　method　was　about　5-8　times　of　that　before　it,　and　both　smallest　and　biggest　value　was　consistent.