A projection apparatus and a heat dissipation control method therefor. The projection apparatus includes a light valve module, a light source providing an illumination beam, a brightness sensor sensing a brightness of the illumination beam, a cooling element having a cold end surface dissipating heat from the light valve module and a hot end surface, a humidity sensor sensing an ambient humidity, a first temperature sensor sensing an ambient temperature, a second temperature sensor sensing a cold end temperature, and a controller coupled to the brightness sensor, the humidity sensor, the first temperature sensor, the second temperature sensor, the cooling element, and the light source. The controller determines a specification temperature according to the brightness, calculates a dewpoint temperature according to the ambient temperature and the ambient humidity, and adjusts a first power of the light source according to the dewpoint temperature, the specification temperature and the cold end temperature.