In Guangxi province, the expansive soil is widely distributed, and the damage to the project is relatively great. It is essential to improve it. Using manufactured sand and water glass as modifiers, in this study, the expansive soil in Nanning, Guangxi was improved under the condition of mixing them separately or in combination. The strength and stiffness of the expansive soil were measured by unconfined compression test and direct shear test. It was found that both manufactured sand and water glass can improve the strength and rigidity of the expansive soil, and both the strength and rigidity first increase and then decrease with increments of the manufactured sand and water glass amount. The manufactured sand will reduce the improvement effect of water glass in the case of compound mixing. The optimum addition amount of water glass is 1%, the optimum addition amount of manufactured sand is 10%. The expansive soil was further improved with manufactured sand of different particle sizes, and it was found that in order to improve the strength of the expansive soil, the particle size of the manufactured sand should not be greater than 0.5 mm. This study verifies the effectiveness of water glass modified expansive soil and manufactured sand instead of natural weathered sand to improve expansive soil, which can provide a reference for future improvement of expansive soil.