The magnetic field of solenoid with length L = 200 mm is discussed in detailby using the Biot-Savart

law and the principle of vector superposition.The magnetic fieldof a single current-carrying circular coil is exactly

derived. Pythonis adopted to integrate the analytical expressions and visualize the corresponding magnetic induction

line. Compared to the classical physics textbooks，both the theoretical derivations and the numerical solutionsare

verifiedvalidly. Then the same analysis are carried out on both the magneticfield and the visualization of magnetic

induction line of a finite current-carrying solenoid. The influence of coildensity and solenoid length on the uniformity

of magnetic field are discussed in detail. It is found that the magnetic field is regarded as uniformity in the range

of -74 mm ≤ z ≤ 74 mm of a solenoid when the density is greater than 1000 m-1 . The results in this paper provide

intuitive and clear teaching materials for theoretical and experimental teaching in College Physics.