The conventional method of raising seedlings with plastic trays has drawbacks, including large plastic tray consumption, difficulty in recycling and potential farmland white pollution, along with high labor input and production costs. To clarify the effects of tray-free simplified rice seedling raising technology, which uses biodegradable biomass seedling films to replace traditional plastic trays on rice grain yield and its components, large-scale comparative field experiments were conducted in seven major rice-producing counties of Heilongjiang Province from 2022 to 2024. Independent-sample t-tests, linear mixed-effects models and structural equation modeling were applied to systematically evaluate the application effects of this technology. The results showed that the average grain yield of the treatment group reached 9032 kg/ha, which was a significant increase of 5.93% compared with the 8526.0 kg/ha of the control group. Compared with the conventional method, this technology markedly increased the effective panicle number, the filled grain number per panicle and 1000-grain weight, and reduced the percentage of unfilled grains, presenting positive yield performance across different regions, although the magnitude of increase varied (2.7–9.5%). Based on the previous literature, this technology has the potential to reduce plastic use and its associated environmental impacts, although direct measurements of carbon emissions and degradation rates were not conducted in this study. Featuring potential ecological benefits and simplified cultivation with prominent yield-increasing effects, it is worthy of popularization and application in cold-region rice planting areas.