round带来的误差吧
  
import numpy as np
np.set_printoptions(precision=10)
mul=np.array([[ 2.79358336e-03, -4.33801272e-03,  1.49405606e-01, -1.49494674e-01],
  [-4.33801272e-03,  6.73628032e-03, -2.32004399e-01,  2.32142708e-01],
  [ 1.49405606e-01, -2.32004399e-01,  7.99047014e+00, -7.99523365e+00],
  [-1.49494674e-01,  2.32142708e-01, -7.99523365e+00 , 8.00000000e+00]])
ceshi = np.linalg.inv(mul)
print(ceshi)
print(np.dot(mul,ceshi))

结果很好。
[[ 9.9999999972e-01  2.2738627202e-09  1.3793326802e-07  3.0552397130e-08]
[-1.9312036348e-08  1.0000000003e+00 -3.5390205509e-08  7.9395173337e-08]
[ 7.9788092474e-07  5.8153643304e-07  1.0000081132e+00 -2.5645946665e-06]
[ 0.0000000000e+00  0.0000000000e+00  0.0000000000e+00  1.0000000000e+00]]
--
修改:control FROM 123.112.65.*
FROM 123.112.65.*