Provided is a method and a system for controlling engine start of a hybrid vehicle based on acceleration demanded power of a driver. More specifically, a variance of an output signal of an accelerator pedal sensor (APS) senses manipulation of an accelerator pedal reflecting an acceleration demand of a driver. When the variance of the output signal of the accelerator pedal sensor is a positive threshold value, acceleration demanded power corresponding to the output signal of the accelerator pedal sensor is calculated in a section in which the variance is positive and the calculated acceleration demanded power is accumulated. The accumulated acceleration demanded power is then compared with a set power value, and the engine is started to switch from the EV mode to the HEV mode when the accumulated acceleration demanded power is equal to or greater than the set power value.