A VOC detecting and warning method is provided. Firstly, an actuating-and-sensing module having a gas transportation actuator and a gas sensor is provided. Then, the gas transportation actuator guides a specified amount of gas to the gas sensor for obtaining plural monitored values, each of which is generated according to a result of detecting volatile organic compounds of the gas in each monitoring time interval by the gas sensor. All the monitored values obtained in a unit time period are added together and calculated, so that an average comparison value is obtained. If the average comparison value is determined greater than an injury threshold defined according to the VOC inhalation amount affecting the health of a human body, the actuating-and-sensing module issues a warning notification to notify the user to take protective measures.