The invention provides a portable device for diagnosis of lung cancer, which comprises a balloon, a gas pump, a buffer gas chamber, a reaction gas chamber, an image collection and processing system and a control system; the balloon collects exhaled gas of a patient with suspected lung cancer to carry out the reaction with a pre-designed porphyrin sensor array (the sensor array for detecting lung cancer markers, if the lung cancer markers exist, the color of the sensor array is changed before and after the reaction) in the reaction gas chamber, the collection of images before and after the reaction is realized by controlling the image collection and processing system through the control system, the images are compared, the collected images are carried out with the pretreatment to obtain the differential images before and after the reaction, the differential images are further compared with data in an expert lesion database to obtain the detection result, and the detection result is finally displayed through a liquid crystal screen or a micro-printer, thereby judging whether the patient suffers from the lung cancer or not.