Analysis on the fluctuation correlation between the international oil price and main grain price are carried on via a type of new network analysis method based on sliding window technique, which can map the fragments of WTI international crude oil futures and the three main crop price series into nodes by using the classical visibility graph construction strategy. Four price fluctuation mode transfer networks are constructed and analyzed on details. Main network haracteristics, as well as 16 higher-order knots existed in the associated modal networks, are discussed, too. Our result shows that, the fluctuation modal transfer networks of the WTI international crude oil futures price, the wheat, the corn, and the soybean price all have similar local structures, which means the WTI international futures price has the same time series evolution characteristics with wheat, corn and soybean price series. It indicates that, there exists a potential linkage between the fluctuation of international oil price and the change of domestic grain price in China. We also founded that, the change of corn price is most closely related to the fluctuation of international oil price. This results is helpful for strategies designing under the viewpoint of stable national grain security. Also, the proposed associated modal transfer network constructing method and the high order knots analysis method used here can be easily extended to similar process for other situations.