Danny Rowe bagged a hat-trick and Saidou Khan notched the other.
The match was interrupted in the second-half when protesting Southend fans invaded the pitch to voice their anger at chairman Ron Martin.
The victory was Town’s first in four and it moves them up a place to fourth in the National League table.
Here are Liam Norcliffe’s player ratings from the game...
5. Jeff King 9
He set up all three of Chesterfield's goals. Played really well against Wrexham in midweek and followed that up with another top display here. Photo: Tina Jenner
6. Curtis Weston 7
He went about his business with minimal fuss. Kept it simple. He was one of three players who had to come off injured. He made his way off with just over 20 minutes to go. Photo: Tina Jenner
7. Jim Kellermann 8
Another inspired performance in midfield after his top showing against Wrexham. Looks a great addition. Photo: Derbyshire Times
8. Calvin Miller 7
A strong attacking performance in the first half from the wideman. Photo: Tina Jenner