An optical scrambler using a whispering-gallery-mode micro bottle cavity is proposed to scramble a complex optical signal to generate an uncorrelated output. We experimentally demonstrated this micro-cavity scrambler by using a chaotic laser light as incident signal and studied the influences of the coupling state. Experiments achieved a fully scrambling with a low cross correlation of 0.028 between the output and the input. Results indicate that the scrambling effect originates from the interference among numerous WGMs in the bottle cavity. It is believed that the micro bottle cavity having an efficient scrambling function can become a promising candidate for encryption.