This document specifies the test devices, test procedures，data analysis, test report，quality control of swelling pressure test for buffer material under coupled thermo-hydro-mechanical conditions for the geological disposal of high-level radioactive waste. This is one of three key tests of buffer material under these conditions. Specifically, the test temperature range of those tests is from room temperature to 90 ℃, because the buffer material will experience such temperature conditions during early disposal process. This document is Part 1 of a three-part series comprising the following: Part 1 – Swelling pressure test Part 2 – Hydraulic conductivity test Part 3 – Triaxial compression strength test The series is applicable to the whole process of testing of buffer material under coupled thermo-hydro-mechanical conditions for geological disposal of high-level radioactive waste. This document is applicable to the swelling pressure test specifically.