I downloaded Graphviz 2.38 MSI version and installed under folder C:\\Python34, then I run pip install Graphviz, everything went well.
1) Graphviz – download unzip in a particular place in the system (pip does not work in windows ) and include the bin folder in the path (‘set environment variables in windows’ OR) set manually in each program
import os
os.environ["PATH"] += os.pathsep + 'C:/GraphViz/bin'
2) Then put the model to plot
clf = xgb.train(params, d_train, 1000, evals=evallist, early_stopping_rounds=10)
xgb.plot_tree(clf)
plt.rcParams['figure.figsize'] = [50, 10]
plt.show()