In the process of crystal growth in solutions, double diffusive convection due to thermal and solutal gradients occurs. A measurement system composed of a rapid heat-transfer control system and an accurate real-time phase-shifting interferometer has been developed to investigate the transient diffusive convection. The heat-transfer control system has a small test-cell in which the liquid temperature is controlled by non-equilibrium thermoelectric devices. In-situ measurement of the transient double diffusive convection and crystal growth rates of NaClO3 are carried out by using this system. Transient double diffusive fields are observed clearly, and the crystal growth rates of the present experiments show similar tendencies to the data of microgravity experiments.