Herein, a pH/ultrasound dual‐responsive gas generator is reported, which is based on mesoporous calcium carbonate (MCC) nanoparticles by loading sonosensitizer (hematoporphyrin monomethyl ether (HMME)) and modifying surface hyaluronic acid (HA). After pinpointing tumor regions with prominent targeting efficiency, HMME/MCC‐HA decomposes instantaneously under the cotriggering of tumoral inherent acidic condition and ultrasound (US) irradiation, concurrently accompanying with CO2 generation and HMME release with spatial/temporal resolution. Afterward, the CO2 bubbling and bursting effect under US stimulus results in cavitation‐mediated irreversible cell necrosis, as well as the blood vessel destruction to further occlude the blood supply, providing a “bystander effect.” Meanwhile, reactive oxygen species generated from HMME can target the apoptotic pathways for effective sonodynamic therapy. Thus, the combination of apoptosis/necrosis with multimechanisms consequently results in a remarkable antitumor therapeutic efficacy, simultaneously minimizing the side effects on major organs. Moreover, the echogenic property of CO2 make the nanoplatform as a powerful ultrasound contrast agent to identify cancerous lesions. Based on the above findings, such all‐in‐one drug delivery platform of HMME/MCC‐HA is utilized to provide the US imaging guidance for therapeutic inertial cavitation and sonodynamic therapy simultaneously, which highlights possibilities of advancing cancer theranostics in biomedical fields. The sonosensitizer loaded mesoporous calcium carbonate nanoparticles decompose instantaneously under the cotriggering of tumoral inherent acidic condition and ultrasound irradiation. The released CO2 and sonosensitizer exploited the merits of synergistic combination of therapeutic inertial cavitation and sonodynamic therapy simultaneously, resulting in antitumor effects with multimechanisms.