<p>In recent years, green certification has been utilised by governments as an important tool to improve the green output of industry. However, the negative impacts associated with the diversity of green certifications (also known as eco-labels) have become increasingly severe over time. Consequently, many government departments have implemented policies aimed at reducing the number of eco-labels by integrating them. Taking China as an example, this study uses an agent-based model that incorporates consumer, firm, and certifier heterogeneity and bounded rationality to investigate whether a standards integration policy can improve green output. The simulation results reveal that when there are multiple eco-labels, firms will choose as many different eco-labels as possible to achieve a competitive advantage, and competition amongst certifiers will cause their certification standards to converge on an intermediate level, resulting in a decline in green output. Moreover, the simulation reveals that standards integration will improve green output only when the government requires standards levels to be within a certain range after integration. And the effects of such policies are influenced by external factors such as levels of consumer confusion about eco-labels, consumer preferences for green products, green production costs, and the distribution of eco-label certifiers in the market.</p>