Traditional rooftop greenhouses offer a promising solution for urban vegetable supply but have the disadvantages of overheating during the daytime and supercooling during the nighttime. To address these issues, a novel solar greenhouse system using nanofluid spectral splitting and phase change materials (NSS-PCMs) was developed. In this study, a 75-day thermal environment test experiment was conducted on the novel solar greenhouse, and the growth status and nutrient composition of three typical plants were evaluated. By optimizing the greenhouse structure parameters through the model, over 80% of 300–800 nm wavelengths for vegetable photosynthesis were transmitted to the greenhouse, while the remaining spectrum was used for heat storage to maintain warmth during nighttime. The novel solar greenhouse reduced daytime temperatures by 5.2 °C and increased nighttime temperatures by 6.9 °C, reaching a maximum thermal efficiency of 53.4% compared to traditional greenhouses. The 75-day temperature detection showed that optimal temperature ranges were maintained for approximately 60 days, both during daytime and nighttime, with an 80% assurance rate. The growth rates of three vegetables in the novel solar greenhouse improved by 55%, 35%, and 40%, and the nutrient composition doubled compared to the control group.