The International Symposium on Numerical Methods in Heat and Mass Transfer 2019 was held in Hangzhou on May 24-26, 2019. Prof Jiangrong Xu and Prof Bingyang Cao serve as the chair of the symposium, which was hosted by the Engineering Thermophysics Society of Zhejiang Province and Hangzhou Dianzi University. In this conference, we have more than 40 Oral Presentations. The research areas cover the heat and mass transfer in low-dimensional, nano and novel materials, the heat management in aircrafts, data centers and vehicles, the exciting studies in multiphase flows, turbulences and renewable energy systems. The heat transfer scale ranges from the smallest quantum level to the macroscopic level, the heat transfer forms range from the phonon and electron conduction, convection, boiling and condensation, frosting and icing to radiation. The research tools include the first principles calculation, molecular dynamics, finite element calculation, machine learning, and the most state-of-art experimental approaches are closely entangled with these numerical methods. We have more than sixty delegates from all over the world, from more than thirty research institutes and industrial sectors.