Laser-based three-dimensional (3D) printing of polymers is a promising technology in fabricating complicated structures for applications in bioengineering, optics and molding. Infrared (IR) laser-assisted thermal curing printing technique offers high controllability by heating up the sample locally. Compared with other techniques like ultraviolet (UV) curing, IR laser-assisted thermal curing avoids yellowing issue, which is a common problem in UV curing. Accurate thermal simulations of the polymer curing processes under the laser heat is crucial to the design and improvement of the printing apparatus. In this work, a multi-physics simulation is carried out to predict the temperature rise and the curing extent profile of polydimethylsiloxane (PDMS) heated by a periodic, pulsed laser. The simulation incorporates the coupling between the local heating and the curing extent change. The cured spot sizes are provided for the given duty cycle and laser pulse period. The exothermic enthalpy of PDMS during the curing process is also measured to improve the simulation accuracy. The simulation results are validated with experiments using a pulsed 2 μm IR laser. This technique can control the polymer curing to achieve a minimum feature size of ~20 μm. Various patterns are fabricated to demonstrate the flexibility of this technique.