To improve the cleanliness of high-quality 51CrV4 spring steel strip， this study systematically investigates the evolution characteristics of inclusions throughout the entire non-steady casting process by industrial sampling experiments， inclusion analysis， and oxygen-nitrogen analysis. The limiting factors and improvement measures for cleanliness are proposed. The results indicate that inclusions in the slab are primarily complex inclusions composed of CaO-MgO-Al

2

O

3

， CaO-Al

2

O

3

， MgO-Al

2

O

3

， and Al

2

O

3

respectively combined with precipitates （MnS， TiN， and CaS）. During RH calcium wire feeding and soft argon blowing， the molten steel experiences both reoxidation and a significant nitrogen pickup. Furthermore， severe reoxidation occurs in the tundish during the first heat， with significant fluctuations in the molten steel level in the early casting stage， leading to noticeable gas absorption and an increase in the number of oxide and nitride inclusions. Consequently， the number of inclusions at the head of the slab formed after casting is relatively high. Adjustments should be made to the RH calcium wire feeding and soft argon blowing processes to reduce molten steel e

xposure. Ensuring the quality of the tundish refractory material during the first heat， extending the argon blowing time before casting， controlling molten steel level fluctuations in the early casting stage， and cutting off the slab head at 3 m from its beginning are recommended.