The CCN (calculate crossing number) algorithm using branch and bound method to calculate the crossing number of graph with small order is put forward to study the crossing number using computer. With the algorithm, the crossing number of all of the 4-regular graphs Aac(n) for n≤12 and the crossing number of some random 4-regular graphs Arc(n) for n≤16 are calculated. At the end of the paper, the average crossing number is shown, and a conjecture is given that the average crossing number of 4-regular graph is O(n²).