The purpose of the study was to test and compare the validity of Satoitem caution index with Harnisch and Linn. item caution index for diagnosisof item patterns of Prathom Suksa five students in mathematics test in term1 (unit 1-8). The sample were four groups of 94 Prathom Suksa fivestudents from primary schools in Srisaket province. The sample obtained bymulti stage random sampling technique, each group took one of four tests:normal test, incomplete of answer test, error check test and higher leveltest. It's finding were as follows: 1. Sato item caution index and Harnisch and Linn item caution indexwere valid for diagnos of item patterns of tests. And disparity coefficientcan be applied validity and reliability with Sato' item caution index andHarnisch and Linn item caution index. 2. Sato item caution index and Harnisch and Linn item caution indexfor diagnosis of unusual item were not different in the validity.