Synthesis of 3-methyl-3-buten-1-ol (MBOH) from thermal condensation of isobutylene and formaldehyde with methanol as solution was studied in this paper. The effect of reaction parameters such as temperature, pressure, isobutene/formaldehyde molar ratio, and reaction time were investigated. The result revealed that the yield of MBOH increased with the temperature at first and then decreased while increased upon increasing of reaction pressure. Under optimum reaction condition of 498 K, 11.0 MPa, isobutene/formaldehyde molar ratio of 9:1 for 6 h, the yied of MBOH could reach 59.24%.